The bellow is for a BIOS password, not for a Windows logon issue, does not apply here.
APPOOS :
I HAVE WINDOWS 7. I HAD THE SAME PROBLEM. IF YOU HAVE ENABLED USER ACCOUNT THIS MAY HAPPEN. PLEASE TRY REMOVING YOUR PASSWORD. AND TRY TO USE A PASSWORD FOR YOUR SYSTEM.
IF YOU ARE USING ASUS MOTHER BOARD DO LIKE THIS
1. WHEN IT IS DISPLAYED 'ASUS MOTHER BOARD.....' HIT DELETE
C-MOS SETTING will APPEAR (A BLUE SCREEN)
-SNIP-
CALCULATION: ONLY FOR ASUS
There is a fix here
http://forums.techarena.in/vista-help/742756.htm about half-way down that involves copying the error log to a different system, checking what files caused the error, and copying the files back over to the original drive, but this involves having 2 computers with the same operating system available and the knowledge to find and copy and read the event log.
Do you have another user account you can try?
Will cost a bit in support hours if you take it to a tech, should be a couple of hundred bucks. If you want to go a cheaper way, get a new hard-drive, install a clean Windows setup on that, and copy your files, favorites, etc.. off the original drive. Your actual files should be fine.