I think you should go here first, the iso version is down the page a bit, http://www.memtest86.com/
-Download memtest86 iso, use nero or another burning program to burn this image to cd.
-put the cd in the computer, reboot, boot into cd by hitting f-8 continously when computer restarts,
-this will run a ram(memory) test, this sounds like a possible memory(ram) problem you are having.
-run this, let us know if this worked foer you or not.