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HP Desktop PCs - Recovering the BIOS (Basic Input Output System)

The BIOS is the first software to run after turning on the computer. If the BIOS on your computer becomes corrupted, the computer fails to boot to Windows.

The BIOS can be corrupted during normal operation, through environmental conditions (such as a power surge or outage), from a failed BIOS upgrade, or damage from a virus. If the BIOS is corrupted, the system automatically attempts to restore the BIOS from a hidden partition when the computer is restarted. If the automatic BIOS restoration does not work, you can manually restore the BIOS.

If you experience any of the following symptoms after restarting the computer, recover the BIOS.

  • Windows does not start and the caps lock or num lock keys blink, or the computer beeps 2 times

  • Power light or charging light continues to blink

  • A BIOS APPLICATION ERROR 501 message is displayed

  • The computer stops at a black or blank screen when powered on

  • The computer turns on and you might hear the internal fan, but the display is blank and Windows does not start

Note:

For business computers, your IT department or local IT service might manage BIOS settings. Confirm this if you cannot access BIOS settings or restore the BIOS.

Reset the Embedded Controller

In some cases, the computer cannot boot to Windows because the data in the Embedded Controller (EC) is corrupted. Use this procedure to reset the EC.

  1. Turn off the computer and disconnect the power cord for 5 seconds.

  2. Connect the power cord to the computer, and then press the power button to turn on the computer.

The computer turns on and the EC is reset.

If this does not recover your computer, see Reset the CMOS.

Reset the CMOS

In some cases the automatic BIOS recovery fails because of corrupted Complementary Metal Oxide Semiconductor (CMOS) data. The CMOS stores BIOS settings. Use these procedures to reset the CMOS and recover the BIOS.

Find the CMOS reset instructions specific to your computer model number

CMOS reset instructions are specific to the system board installed on your computer. Find your computer model number, and then use it to get the reset steps (if available) on the HP Customer Support website. If steps specific to your system board are not available, use the generic CMOS reset steps.

  1. Locate the model number for your computer. This number is typically found on a label on the computer or on the box it shipped in. Go to How Do I Find My Model Number or Product Number? for additional options.

    Note:

    The general or series name on your computer is not specific enough for identifying the correct computer specifications.

    Computer label with the product and model numbers highlighted
  2. Go to the HP Customer Support website, and then use the model number to navigate to the product page for your computer.

  3. Select Product Information, and use the drop-down menu to select Product Specifications.

  4. Open the product specifications and find the motherboard section.

  5. Click Motherboard specifications, if a link is available, to find the CMOS reset steps. The steps for resetting the CMOS might be called Clearing CMOS or similar.

  6. Go to Reset the CMOS using motherboard specifications to reset the CMOS using the specific reset steps for your system board.

    Note:

    If specific CMOS reset steps are not available for your system board, see Reset the CMOS using generic steps.

Reset the CMOS using motherboard specifications steps (recommended)

Use the CMOS reset steps from the motherboard specifications to reset the CMOS and recover the BIOS.

  1. Turn off the computer, and then disconnect the AC adapter from the desktop.

  2. Press the power button 10 times to fully discharge electricity from the system.

  3. Open the computer to access the system board.

  4. Follow the CMOS reset steps for your computer model. See Find the CMOS reset instructions specific to your computer model number.

  5. Reassemble the computer.

  6. Reconnect the AC adapter to the computer.

  7. Press and hold the power button for 20 seconds.

  8. Release the power button and the system boots.

A message displays confirmation that the CMOS is reset. The message on your computer might vary. If this does not recover your computer, see Recover the BIOS.

Reset the CMOS using generic steps

If specific CMOS reset steps are not available for your system board, reset the CMOS and then recover the BIOS using these generic steps.

  1. Turn off the computer, and then disconnect the AC adapter from the desktop.

  2. Press the power button 10 times to fully discharge electricity from the system.

  3. Open the computer to access the system board.

  4. Remove or disconnect the CMOS battery from the system board.

    Example of CMOS battery types
  5. Confirm that all sources of electricity are removed or disconnected from the computer, including the CMOS battery.

  6. Press the power button for a minimum of 60 seconds to drain all power from the computer and reset the CMOS values on the system board.

  7. Reconnect or reinstall the CMOS battery, and then reassemble the computer.

  8. Reconnect the AC adapter to the computer.

  9. Press and hold the power button for 20 seconds.

  10. Release the power button and the system boots.

    A message displays confirmation that the CMOS is reset. The message on your computer might vary.

  11. Confirm the that Time in BIOS is set to 00:00. If not, perform the procedure again, but hold the power button for 120 seconds at Step 6.

If this does not recover your computer, see Recover the BIOS.

Recover the BIOS

If your computer BIOS still does not reset, you can try to recover the BIOS using a key press combination or a USB recovery drive.


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