PC problem

[munky]

I've been taking a look at my dad's PC, a Dell dimension 5000 which appears to freeze after it has been on a while.. looks like a case of overheating to me but with no obvious reason. When it did freeze up, I opened the case and the CPU heatsink was really quite hot, and yet the fan never speeds up. I tried downloading a few utilities that monitor CPU temp, but none of them can detect a CPU temperature sensor; then find the sensors on the hard drives but that's it. It's a pentium 4 HT processor, is it possible there's no temp sensor or that it's not working?
Anyway I did find a utility that allows one to force the fan to speed up, but as nothing can detect the CPU temp I can't get it working automatically. Any ideas as to what the cause of the problem is or a better way to rectify it? It's not blocked with dust or anything, it just seems that (apart from using this manual override) the fan just sits there idling no matter what load the CPU is under. thanks!

[munky]

MiniMac said:

Fan def plugged into mobo? Swap fan? PSU not providing enough power. Locks up when PC is idle or under heavy load?

Fan is definitely working, just seems to be very low rpm. It's spinning a lot faster now that I'm forcing it to - but of course now it's noisy all the time. Seems to lock up when it's under some load, e..g when running a spyware scan, rather than when it was completely idle.