I usually leave my PC on at night.
However, one day last week I woke up to find that the computer had been turned off. I came closer to the machine and noticed that the LED was still on, despite all internal fans being off. This was a very, very, bad sign.
I turned the computer PSU off and on again. The computer lit up, all was going fine. For all of 1.5 seconds. Next thing I know the thing powers off and a very suspicious odor eminates from the case. Not good.
Needless to say, the PSU blew. Through testing though, I found out that all other parts were okay. *sigh of relief*. Last Friday, I went out and got a new PSU (Antec SmartPower 500W). I figured that this was a ventilation issue, due to me cramming so much equipment in the last case. So I got a bigger case as well. Small problem: now my IDE cables were too short.
As I was working the weekend, I had to wait until Monday to buy the new cables. Installed it all, and it now works well.