I can't find how to access the BIOS on your computer, but normally rapidly pressing "delete" or "F1" or "F2" when you turn the computer on will do it.
If you haven't tried safe mode yet, start you computer and rapidly press "F8", this will give you a menu so you can boot Windows into "Safe Mode" and hopefully fix your problem.
As a last resort, you may have to reinstall Windows (without doing a format), in order to fix your problem, or at least so you can back up anything on your computer before you do a format.