It probably keeps frying because the computer is in a cubby hole in a computer desk and it gets too hot.

It might be that. On the other hand, it might be bad power. Either way, I'd be wary of this. I've had PSUs that have failed on, rather than off, meaning that they dump a metric shitload of juice through the mainboard and fry everything. At that point, you've got no choice but to upgrade.