This is a follow-up to this thread:
http://ubuntuforums.org/showthread.php?t=2082434

I have a Ratel Ultra desktop which is a little over a year old (out of warranty). I installed a new version of Ubuntu as suggested, the system continued to shut down, I sent the computer in to System76, and they said the hardware looked fine and they were able to start it up with no problem, so they sent it back.

So I set it back up and plugged it in yesterday and it started up, but it's still randomly shutting down. This time, I got an error message on one occasion that said "thermal event (overheating)", and after googling, it seems that random shutting down is a typical symptom of an overheating problem, so I think that's probably what's going on. I opened the tower, vaccuumed the CPU fan, but other than that, I don't know what I should be looking at (and I can't spend another $90 to send the computer off again without it coming back working).

I'm not sure where to post for help. System76 has already looked at the computer, so this issue is not necessarily relevant here, although the hardware was put in by System76, so maybe it is relevant here, as knowledge of the hardware specifics could make it easier to pin down an issue? Would it be more effective to post in the Hardware area of the Ubuntu forum?