The computer i've been using for the last 3-4 years has just started crashing but only when i was playing a few select games. It happened because of a heat issue and all i had to do is open up the case and blow out all the dust and get 2 more fans for the case. I noticed when i first got this computer my processor would run at around 38~c and now even at idle it's around 54~c. I don't know what your processor is but try downloading a program called "Speedfan" and try to get your CPU temp and report back, It could be bad memory, overheating Cpu, or overheating Gpu if you have one installed or a number of other things.