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Archive for September, 2010

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