Recovery Password

I have a E-Machine who has gotten a hold of a virus that won' t allow me to start up. The virus has been referred to as the "Black screen of death" any way short of reformatting and loosin everything I am trying to use my windows xp disc and the option of the recovery system, but it keeps asking me for my adminastrative passord, I didnt set up any passwords so I have no idea what it is referring to. if I leave it blank "which I have been told to do" it agian ask for the password, doing this 3 times results in restarting the PC. Any ideas or suggestions would be great. Thanks

 

I have used ophcrack with good results for retrieving passwords:
http://sourceforge.net/projects/ophcrack/

You could give it a try.