Is there anything else on the blue screen, or just the Stop code? Any file names or other information?
Test your RAM one stick at a time using a Memtest CD.
Direct link to pre-compiled bootable ISO for Memtest:
http://www.memtest.org/download/2.01...+-2.01.iso.zip
Unzip the file and burn the ISO to CD (as an image, not as data) to create a bootable CD. Reboot and go into the BIOS. Change the boot order to 'CD first', save settings, insert the CD and reboot. This will start the program. Run for one stick at a time (very important, to prevent false readings) for at least 10 passes each.