4 ways:
1) Enter safe mode through F8 before loading to see if you can bypass that blue screen.
2) Run Microsoft Security Essentials which is included in your OS to detect any spyware/virus.
3) If you can't access your HDD at all due to blue screen, try to slave your bad HDD and test out with another HDD. If it's successful you can at least retrieve important files from the other HDD.
4) Lastly, you can always re-install windows and reformat from Bootup to get a fresh clean copy OS. Good luck!