Run a memory test:
http://www.howtogeek.com/howto/windo...agnostic-tool/
Windows Vista/7 include it with the bootloader now. If the test shows bad RAM get it replaced.
Make sure your drivers are up to date as well.
Feel free to get us a screenshot of the BSOD using this:
http://www.nirsoft.net/utils/bluescreenview.zip