I have a Compaq Presario 5000 Pentium 4. Lately it has been shutting down on its own. I noticed that the power supply fan never comes on. In my experience, at least with store bought computers that the fans almost always run. Never the less I tried it with another aftermarket power supply and it wouldn't even power up. I'm not above buying another one to fit it but I just wanted to see if anyone else knew whether or not the fan should at least kick on at some point. Thanks in advance.