Whirring noise

Good Morning. My issue is this. Either while the computor is idle, no one on it, or while someone is working on it, at random, the computor sounds like it is powering up, yet there is nothing going on. I have checked task manager for cpu usage, but I keep missing whatever it may be in there if anything at all. I have a good report with adaware and spybot. Avg shows good also. I have no way to check heat temps in case that may be an issue. I have only two fans, one cpu, the other power supply. I keep the dust out of the case on a regular basis. I have no idea where the noise is coming from. It also occurs when a cd, or dvd opens and loads. My machine is a compac presario sr 1800 nx running Windows XP2. Tats about all I can tell you at this time. Would anyone have any ideas on what could be happining. As always, thanks in advance.

 

plod: sounds like a drive: ie: like the sound a cd/dvd drive make when a cd is inserted and powering up

 

Look here

http://forums.majorgeeks.com/showthread.php?t=148909