Quote from DisciplinedHedg:
The PSU was a Rosewill 500W. It was highly rated at Newegg at the time and had more than enough juice.
The computer now starts and powers up. But sometimes it will reboot at any time, or display all kinds of different gibberish on the screen.
Is this (along with the couple of firecracker pops somewhere in the case) consistent with a failed PSU?
In that case, probably not. What it could be is a "heat" issue. I'd check to see what the core temps are when you get up and running at normal load. Perhaps, the interior has collected alot of dust or the heatsink and cpu fan aren't properly cooling the system and once it reaches a certain temp, the pc will automatically shut off to not do any more damage.
I'd argue that's a probable cause.
