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Cracking a BIOS password

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Someone in my family owns an older laptop, but they have lost the BIOS password. You can boot into Windows XP, but you can not enter the BIOS Setup (e.g. for changing the order of boot devices) without password.


I found a tool called CmosPwd which tries to decrypt BIOS passwords. However, there was a problem: it only runs on DOS.  Therefore I took a DOS boot floppy disk image and added CmosPwd to it (you can use e.g. MagicISO to edit floppy images).

But how to boot a floppy disk image when the machine boots directly into Windows XP? ¬†You can instruct the NTLDR (XP’s bootloader) to boot Grub4DOS instead of the Windows kernel and use Grub4DOS to load the floppy image into memory and boot from it. Copy the floppy image, grldr from Grub4DOS to C:, edit your boot.ini and create a menu.lst.

Finally you just need to reboot the machine, select Grub4DOS in the boot menu, and run cmospwd.

Written by johnLate

September 9th, 2010 at 8:27 pm

Posted in Uncategorized

2 Responses to 'Cracking a BIOS password'

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  1. I know some methods to reset bios password.

    1. The best and easiest method: Close OS and shut down the electricity power of computer. Open your computer box, take out the cmos battery from the mainboard. Then the bios password will be reset to blank. Put it back after a few minutes.

    2. Follow some hard tutorials, it is difficult to do. It is better that you are a expert. For example this tutorial: Bypass BIOS Password or Crack CMOS Password?

    So I would suggest you the 1st method. Hope it helps.


    10 Sep 10 at 08:17

  2. There were several reasons against your method nr 1:

    – I was curious what the old password was.
    – I didn’t want to lose any other bios settings.
    – I didn’t want to take apart the laptop to locate the bios battery.

    The tool mentioned in your link is sold for $25, CmosPwd is free.


    10 Sep 10 at 16:15

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