Dude, same thing happened to me a few weeks back. My registry got fucked up (not from a virus, but a program crashed and couldn't recover and Windows didn't know what to do and just tossed part of my registry), and every time I tried to log in to my account it would crash the computer again. Ultimately I had to back up my files and then reinstall Windows with the installation discs that came with my computer.
This will definitely solve things, but it might be way more work than necessary. First, take note of the error message that appears on the blue screen (like, 'IRQL_NOT_LESS_OR_EQUAL') followed by the 'STOP' code after it (like '0x00000050' followed by more numbers in parenthesis), as these will pinpoint the exact problem. A Google search on the code (on a different computer) can often provide you with a course of action. Also, try these forums for direct assistance:
http://www.bleepingcomputer.com/forums/