CPU Fan Spinning before power on??

[ishamy]

Hi all I'm trying to fix a problem with a pc, basically it was shutting down after 10mins use, I opened it up and basically I was lifting the dust out, that was that sorted the second problem is that when you plug in the pc and switch on at the wall the cpu fan starts spinning, this is before the PC power button is pressed.

The PC is by Aria looks like a throw it together company.
The mobo is a Asrock K7VM2
processor is AMD Athlon XP 2400+

Thanks for any help.

 

[Corasik]

Does it spin for a second and then stop, or does it spin all the time when mains power is on. If its the former, its just a surge as you click on the mains safe to ignore.

If its the latter, then it could be a fault on the motherboard a short between 5vSB, and the cpu fan header for example.

Is it just the cpu fan, or do any of the other fans spin up (PSU etc)