This really does sound like a hardware issue to me, as well.
Memory is definitely a candidate for this type of behavior.
I while back, mine did the same thing. Tried everything, including adding memory. Still did it...untill I did some research and found an online article describing the exact problem and the solution. Motherboard CAPACITORS. Sure enough, on examination of the MOBO, I had 6 large and 5 small capacitors with bulging tops and leakage. This can be typically found on older computers, especially those that were econo type computers, as the mobo manufacturer would buy the cheapest capacitors they could.
The problem is so typical, that there are vendors on ebay that sell prepacked sets of these capacitors in a range of sizes and values. Cheap too, but good capacitors. If you are daring, and have a good low temp soldering iron, its really not difficult. Even I was a little apprehensive about removing my motherboard and the processor. But, like many people, I had no choice because I had no money to replace the motherboard or computer. I really thought this was enevitablly going to fail, as computer mobo's are complex and circuitry so small. But after reading the article, I decided to go for it and what do you know...it WORKED
...to the point I'm still using this old Pentium 4, and that was 3 years ago.
But yea, memory may do it, a reformat and fresh OS install, or even a new Graphics card(must be OpenGL 3.1 compliant). But if you are like me, and have a financial limitation, you might try my solution. I don't have the link anymore, but do a search on MOTHERBOARD CAPACITORS. It just might save the day...er..computer.
and btw..here is proof.
Oh, I forgot..this solution was AFTER I replaced the Power Supply and bought a new hardrive.