My brother's cpu, cpu fan, and hard drive randomly shuts off at random times, like I can get it to start to boot then the cpu and hard drive will shut off but other components will still have power, like the cd-rom drive doors will be able to open and close but the hard drive and cpu shut completely off. Sometimes it lets it boot compeltely but it still the cpu and HD shuts off. I dont know the computer specs but I will check when I get home. I dont think i explained it well enough but if anyone can offer any suggestions it will be apprecaited. thanks

Does it shut off in BIOS?

Does your BIOS have a facility where you can check the CPU temp?

Is the cpu and hard drive actually 'shutting off' or is it just the display which is disappearing?

Assuming that the machine IS shutting down but the fans are staying on, that would point to possible mobo or PSU problems.

Its actully hard to explain, but sometimes the hard drive and process do not stay powered on long enough to even give me the option to go into BIOS and its not over heating because it wont stay on long enough to genterate enough heat to cause a problem. But when it shuts off all the fans but the Power supply fan quits working. The hard drive actully shuts off it stops spinning completely so does the processor fan.

I think it's the way you're describing it that made me ask. I'm not sure how you can tell the CPU (as in the chip inside) is shutting down, so I wanted to find out.

As I see it - and correct me if I'm wrong - the problem you have is that the machine (as in the tower or case, which you're calling the 'cpu') is shutting down but you can still hear fans, yes? You turn it on, it shuts off, but fans are still running? But not every time.

Does it do it when nothing is plugged into it except power (and maybe monitor)? That'll eliminate anything on the outside.

What PCI or AGP cards does it have fitted?

Thing is, something's wrong and you've got to try and pinpoint it to fix it.

CPU's and hard drives don't shut off without being turned off. My guess is your having a power supply problem . If you have a spare one or can remove one from another machine, then put a known working one in and see what happens. Or, you can buy a power supply tester at most computer stores. I like to have some spare parts around just for this purpose so buying one to keep around isn't a bad idea, in my view.

It could be some kind of short circuit in your mobo causing the problem like a screw that has come loose or something similar. you might want to open the case and just have a look for something like this just incase.