Dude, with all due respect, you need to do some digging and work yourself on this issue. We can't diagnose your problem 100% over the internet. The consensus of this thread is that it sounds like a PSU issue, so what I would do is try a new PSU.
Again, you need to do some work on your own here. We can only speculate on the problem since we don't have the ability to do anything hands on, obviously. And since we don't have hands on use of the PC in question you'll need to do some trial and error type of diagnosis. IE, test components one at a time until you find the fault, whether it is RAM or the PSU. I definitely vote for the PSU but I obviously cannot confirm that, so this is where you have to take the initiative and do the rest. We can't give you a completely correct answer, only speculation.