Well, this is tricky situation. Typically you may want to begin by finding out if it's a memory related problem. DocMemory PC Memory Diagnostic software ( http://www.simmtester.com/page/products/doc/docinfo.asp )is designed for this very purpose. You can start by downloading a copy of the sofware from DocMemory Diagnostic Site , follow the setup instructions and run a diagnostic test on your PC memory.

If all Memory tests results returns good, you will need to isolate and examine other possiblities such as CPU, Motherboard or other peripherals that you have in your PC.