Computer Bios Problems And Solutions

What is BIOS in simple words?

BIOS, computing, stands for Basic Input/Output System. The BIOS is a computer program embedded on a chip on a computer’s motherboard that recognizes and controls various devices that make up the computer. The purpose of the BIOS is to make sure all the things plugged into the computer can work properly.

As your PC’s most important startup program, BIOS, or Basic Input/Output System, is the built-in core processor software responsible for booting up your system. Typically embedded into your computer as a motherboard chip, the BIOS functions as a catalyst for PC functionality action

What is the main function of BIOS?

A computer’s Basic Input Output System and Complementary Metal-Oxide Semiconductor together handle a rudimentary and essential process: they set up the computer and boot the operating system. The BIOS’s primary function is to handle the system setup process including driver loading and operating system booting.

Why do we need BIOS?

We need because, BIOS initializes and tests the system hardware components. Its goal is to ensure that the components are attached, functional and accessible to the Operating System (OS). In case any hardware component isn’t accessible, BIOS pauses the booting process and issues a warning.

Can a computer run without BIOS?

It allocates the hardware resources required for the software to run. It is highly impossible to run a computer without ROM BIOS. … Bios was developed in 1975, before that a computer would not have had such a thing. You have to see the Bios as the basic operating system.

What happens when you reset BIOS?

Resetting your BIOS restores it to the last saved configuration, so the procedure can also be used to revert your system after making other changes. Whatever situation you may be dealing with, remember that resetting your BIOS is a simple procedure for new and experienced users alike.

How to Reset BIOS

Method #1: BIOS Menu

By opening the BIOS menu and finding the Default Settings option, you can reset the BIOS directly from its menu.

To do so, follow these steps:

  1. Restart your computer
  2. Notice the key that you need to press at the first screen. This key opens the BIOS menu or “setup” utility.
    For example, here’s how this looks like on many Dell PCs:Dell BIOS screen showing special key optionsNotice the key guide in the top-right corner.This key is usually any of the following, depending on your computer manufacturer: EscDelF2F8F12.
  3. Find the option to reset the BIOS settings. This option is usually called any of the following:
    • Load Default
    • Load Fail-Safe Defaults
    • Load BIOS Defaults
    • Load Default Settings
    • Load Setup Default
    • Get Default Values
  4. Save these changes
  5. Exit BIOS

Method #2: Clear the jumper

Your computer’s motherboard has a special jumper that can clear the BIOS saved settings and revert them to their original values.

By clearing the jumper, you can also reset the password for the BIOS menu.

To do so, follow these steps:

  1. Shutdown your computer
  2. Flip the power switch so that the computer receives no power.
  3. Make sure you are grounded. Static discharges can damage your computer.
  4. On the motherboard, find a jumper that’s named like any of the following. (This jumper is usually placed near the CMOS battery.)
    • CLEAR
    • CLR CMOS
    • CLR PWD
  5. Set the jumper to the Clear/CLR position
  6. Power on and start your computer
  7. Once your PC has booted, turn it back off, move the CLR jumper back to its original position. Otherwise, each time you reboot, your settings (and clock) will automatically reset!

Method #3: Replace the CMOS battery

If Method 2 above
doesn’t work (your computer doesn’t have the mentioned jumper), you can also try to remove and replace the CMOS battery. This method works if your computer has a CMOS battery. Not all motherboards have that battery. To reset the BIOS by replacing the CMOS battery, follow these steps instead:

  1. Shutdown your computer
  2. Remove the power cord to make sure that your computer receives no power.
  3. Make sure you’re grounded. Static discharges can damage your computer.
  4. Find the battery on your motherboard
  5. Remove it. If the battery doesn’t move easily, stop following this method to reset the BIOS, go to Method 1 or method 2
  6. Wait 5 to 10 minutes
  7. Put the battery back in
  8. Power on your computer

How to enter your PC’s BIOS

Need to change your computer’s boot order or access other advanced settings? Here’s how to access the BIOS (basic input/output system).

Step by Step: Entering the BIOS

1. Get ready to act quickly: You need to start the computer and press a key on the keyboard before the BIOS hands over control to Windows.

2. Boot (or restart) the PC: Pay close attention to the first screen that appears. Look for a message that indicates which key you need to press in order to access the BIOS. That key is likely to be:

–A Function key (such as F1F2, or F3)

–The Esc key

–The Delete key

On some PCs, entering the BIOS may require pressing another key or a combination of keys. Keep your eyes open for an on-screen message that says something like:

–‘Press F1 to enter setup’

–‘BIOS settings: Esc’

–‘Setup = Del’

–‘System configuration: F2’

If you don’t catch it the first time, simply try again. Your computer’s documentation may also tell you which key to press.

3. When you know the right key, start the computer again and press the key when the first screen pops up: You may hear a confirmation beep or see a new message. If you timed it correctly, you’ll be in the BIOS within a few seconds.

BIOS Startup Error Messages and Solutions

When a system has problems starting, it might display error messages at startup. These messages might come from the system BIOS (ROM BIOS or UEFI firmware) or might be generated by Windows. Typical error messages displayed by the BIOS include the following:

  • Invalid system disk
  • Boot failure
  • Hard disk error
  • NT boot loader missing
  • Missing operating system

These and similar messages indicate that the BIOS or UEFI firmware chip on the motherboard cannot locate startup files for your operating system. Possible reasons can include the following:

  • A nonbootable drive containing media is listed first in the boot order (BIOS/UEFI).
  • The computer’s system drive is not properly identified (BIOS/UEFI).
  • Data or power cables from the internal hard disk to the motherboard are loose or have failed (hardware).
  • The drive has failed (hardware).

These are listed in order of likelihood. As always, start with the simplest possibility: You’ve left a USB thumb drive plugged into your computer.

Disconnecting USB Drives

If your system is configured to use USB drives as the first bootable device and you leave a nonbootable USB flash drive plugged into your system (either directly or into a USB hub connected to your system), your system won’t boot. Solution? Unplug the drive and restart your system.

If your system restarts correctly, you have a couple of choices:

  • Don’t leave USB flash drives plugged into your system when you shut down the computer.
  • Change your BIOS or UEFI firmware settings to skip USB drives as bootable devices.

Checking and Changing Drive Boot Order

Should you change the boot order? It depends. More and more diagnostic programs can be run from bootable USB flash drives, and you can also install new operating systems from bootable USB flash drives. However, you can also use your system’s DVD or BD (Blu-ray) drive for these tasks. So, it’s up to you.

We recommend changing the boot order on Windows 7 computers if

  • You use USB flash drives to speed up your system using the Windows ReadyBoost feature.
  • You frequently use USB flash drives to shuttle information between computers.
  • You frequently use USB flash drives for other reasons.

However, you should leave USB flash drives at the top of the boot order if

  • You frequently run diagnostic programs from a bootable USB flash drive.
  • You install operating systems from a bootable USB flash drive.
  • You seldom or never use USB flash drives for data transfer.

If you change the boot order to remove USB flash drives or put them after the system hard disk, you can always change the boot order in the future to place USB drives first if you need to run diagnostic programs or install a new operating system.

Here’s how to change the boot order in Windows 7:

  1. Click Start.
  2. Click the right arrow next to the Shut Down button.
  3. Select Restart.
  4. After your system restarts, press the key that starts the BIOS or UEFI firmware setup program On some systems, such as HP Pavilion DV6 laptop, you might need to press a key (ESC) to see startup options including BIOS setup (F10).
  5. Navigate to the dialog used to set the drive boot order.This system looks for USB thumb drives as the first bootable devices.
  6. Change the boot order to place the optical drive first, followed by the hard disk.
  7. Save your changes and restart your computer.

Windows 8.1 (unlike Windows 8) does not support the creation of a CD or DVD repair disc, although you can use your Windows 8.1 distribution media as a repair disc. With Windows 8.1, if your system supports booting from a USB drive, you should create a USB recovery drive instead.

STOP (Blue Screen) Errors at Startup

If you turn on your Windows computer and, instead of seeing the Windows login screen or desktop, you see a screen similar to the one shown as bluescreen you have a STOP error, also known as a “Blue Screen” or BSOD (“blue screen of death) error. What happened?

 An 0x7B STOP error in Windows 7 caused by changing the SATA interface setting in the system BIOS (a). Windows 8 displays a different STOP error (b).

Blue-screen errors can be caused by many problems. At startup, they’re typically caused by problems with hard disk device drivers. If a blue screen error appears after you have booted to the Windows desktop, it could be caused by corrupt apps, corrupt device drivers, or memory problems.

When you see a BSOD error, be sure to record the numbers listed after the STOP message, such as STOP: 0x0000001E, or 0x1E for short. If the name of the error is displayed, such as KMODE_EXCEPTION_NOT_HANDLED, record it as well. You can then look up the error number and name on the Microsoft Support Site ( to find Microsoft’s suggested solutions.

Table 8.2 lists some of the most common STOP errors and possible solutions.

Table 8.2 Common Windows STOP Errors and Solutions

STOP Error NumberSTOP Error NameSuggested Solutions
0xAIRQL_NOT_LESS_OR_EQUALCheck device drivers or services used by backup or antivirus utilities.
0xD1DRIVER_IRQL_NOT_LESS_OR_EQUALCheck device drivers or services used by backup or antivirus utilities.
0x1EKMODE_EXCEPTION_NOT_HANDLEDIllegal or unknown instruction; check the driver referenced in the error message.
0x24NTFS_FILE SYSTEMTest the hard disk for errors.
0x2EDATA_BUS ERRORTest memory modules; disable memory caching in system BIOS; check hardware configuration.
0x50PAGE_FAULT_IN_NONPAGED AREACheck printer drivers.
0x7BINACCESSIBLE_BOOT_DEVICEIncorrect or missing hard disk device driver; see “Fixing 0x7B Errors,” this chapter, for details.
0x7FUNEXPECTED_KERNEL_MODE_TRAPTest hardware and RAM; check SCSI configuration if in use; make sure CPU is not overclocked.
0x9FDRIVER_POWER_STATE_FAILURECheck power management and CD-writing software; disable power management temporarily; reinstall or upgrade CD-writing software.
0xC21ASTATUS_SYSTEM_PROCESS_TERMINATEDReinstall third-party programs; use System File Checker with the Scannow option (SFC/Scannow) to check system files.

Unfortunately, Windows is typically configured to restart the system immediately when a STOP error is displayed, so you can’t read it. To configure Windows so that a STOP error stays onscreen so you can determine what it is and look for solutions, see “Preparing a Windows-Based Computer or Tablet for Easier Troubleshooting,” Chapter 1, p.37.

You can also disable rebooting in case of a STOP error with the startup option to Disable Automatic Restart After Failure or Disable Automatic Restart on System Failure. See “Disable Automatic Restart on System Failure,” this chapter, p.222.

Fixing 0x7B Errors at Startup

If you are building a computer, have just upgraded to a new hard disk, or have just replaced the motherboard battery that maintains system settings, it’s possible that your computer has “forgotten” the correct hard disk configuration settings.

Almost all hard disks are configured using Auto as the hard disk type. Thus, if the setup information is lost, the default (normal) setting is Auto and the drive will be properly detected.

However, the setting for the SATA interface used by your hard disk can be a problem. There are several possible settings for the SATA interface (IDE, AHCI, and RAID), and if your system is configured using one setting, but a different setting is used in the system BIOS or UEFI firmware, your computer won’t start, displaying a 0x7B STOP error.

If you know the correct setting, follow these steps:

  1. Shut down the computer and restart it.
  2. Start the BIOS or UEFI firmware setup program.
  3. Change the SATA setting to the correct value.
  4. Save settings and restart the computer.
  5. Select Start Windows Normally if prompted.

If you don’t know the correct setting to use in step 3, choose IDE (also known as ATA or Compatible) if the system is set to AHCI, or AHCI if the system is set to IDE, ATA, or Compatible.

Switching to AHCI Mode in Windows 7 and Windows 8.x

If your SATA drives are currently set to run in IDE mode, but you are planning to install an SSD, keep in mind that an SSD cannot provide you with faster performance unless you use AHCI mode. If the system crashes when you change SATA modes, how can you safely change from IDE to AHCI mode?

AHCI mode is also recommended for full performance with SATA 3Gbps and 6Gbps hard disk drives.

Before you make the switch, you need to enable Windows to use AHCI drivers when necessary.

The easiest way for Windows Vista and Windows 7 is to use the Fix-It wizard available from This page also details manual Registry changes that make the same changes as the Fix-It Wizard.

After you run the Fix-It Wizard or make the needed changes manually, you can safely enable AHCI mode in the system BIOS or UEFI firmware setup dialog and your system will install the appropriate drivers and run properly.

To switch from IDE mode to AHCI mode in Windows 8.x, follow this procedure (adapted from

  1. Search for and run msconfig.exe.
  2. Click the Boot tab.
  3. Click the empty Safe Boot box . Make sure Safe Boot is checked before you click OK.
  4. Click OK.
  5. Swipe from the right or move your mouse to the lower-right corner of the screen and click or tap Settings.
  6. Click or tap Change PC Settings.
  7. Click or tap Update and Recovery.
  8. Click or tap Recovery.
  9. Click or tap Restart Now  Restart Now enables you to change firmware (BIOS/UEFI) settings.
  10. Press the key or keys needed to enter the UEFI firmware setup program.
  11. Change the SATA mode to AHCI  Preparing to change a system configured for IDE mode to AHCI mode.
  12. Select the option to save changes and restart your computer.
  13. Search for and run msconfig.exe.
  14. Click or tap the Boot tab.
  15. Clear the Safe Boot check box.
  16. Click or tap OK.
  17. Open the Charms menu.
  18. Click or tap Settings.
  19. Click or tap Power.
  20. Click or tap Restart.

Your computer will restart using AHCI mode for full performance of your SATA devices.

Loose Drive Data and Power Cables

The interior of a desktop PC is a cluttered place. Whether you had your system opened up for a memory upgrade, component replacement, or just to see what’s “under the hood,” you might have loosened or disconnected the power or data cables going to the hard disk or the data cable connecting the hard disk to the motherboard. If your system (C:) drive has disconnected or loose cables, you will see No Operating System or other similar error messages.

Most SATA data cables do not lock into place, so it’s easy to have a loose cable on either a drive or the motherboard

Loose data cable on an SATA hard disk.

 An SATA motherboard host adapter with a loose data cable.

 Some motherboards use front-mounted SATA ports, like this one, which also features a loose data cable.

Similarly, SATA power cables can come loose from drives (see 

The power cable on this SATA drive is not connected tightly.

To solve problems with loose or disconnected cables:

  1. Shut down the computer.
  2. Disconnect the power supply from AC power.
  3. Open the system.
  4. Check the hard disk or SSD for loose or disconnected cable(s).
  5. Check the motherboard for loose or disconnected SATA data cables.
  6. Securely plug the cable(s) into place. A SATA hard disk with properly connected power and data cables. A correctly installed SATA data cable plugged into a top-facing motherboard port.A correctly installed SATA data cable plugged into a front-facing motherboard port.
  7. Close the system.
  8. Reconnect the power supply to AC power.
  9. Restart the computer.

Drive Failure

If your hard disk is making a loud or rattling noise when it’s running, it has probably failed. If the hard disk was dropped or smacked hard, a failure is very likely.

However, a hard disk might have failed if it is absolutely silent even when you place your ear next to it or does not get warm after the system has been on for several minutes.

Before assuming a hard disk has failed, perform this isolation test to determine whether the problem is the hard disk, its power cable, or its data cable:

  1. Shut down the computer.
  2. Disconnect the power supply from AC power.
  3. Open the system.
  4. Locate the power cable running between the hard disk and the power supply.
  5. Disconnect the power cable from the power supply.
  6. If the power cable used a splitter or converter to provide power to the drive, plug the drive directly into the power supply (if possible). If that is not possible, replace the splitter or converter and make sure it is securely plugged into the power supply lead and the drive.
  7. Reconnect the power supply to AC power.
  8. Restart the computer.
  9. If the drive is still not working, repeat steps 1 and 2.
  10. Reconnect the drive to the original power cable (and splitter or converter).
  11. Remove the data cable from the hard disk drive and the computer.
  12. Install a known-working replacement cable.
  13. Plug it into the SATA port on the motherboard and drive.
  14. Repeat steps 7 and 8.
  15. If the drive is still not working, the drive has failed. Replace it.


If you have backed up your information, you can replace your hard disk and restore your system from a backup. However, if you have no backup and the information is vital, you can use a data recovery company to recover your data. These companies have clean rooms that enable safe replacement of failed components and advanced data-extraction techniques. Expect to pay hundreds of dollars for recovery – if the drive’s condition permits it.

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