i have a dell inseron 1525. had a problem with vires . I went to reformat drive and the bios was changed and the harddrive was locked and i dont have password need fix.i have vista will not boot and can't reformat drive .
you can try a program called orphcrack(just type it in a search engine) to see if it can sniff out the system password.
Otherwise you can try to unplug the cmos battery (the coin-celled battery on the mainboard) and start your computer. Shut down your computer and reinstall the cmos battery and that should clear the password.
**note** this only works on some systems. If this doesn't work you will have to contact dell to see if they can help.