computer revving up

[thundercrack]

hi, my computer, when left alone doing nothing( that I know of ) starts racing and whirring, then slows, then speeds up again( the hard drive ) .
i press alt cont del and it shows nothing active, but shows the cpu at 40% then 10% then up then down and finally 0 %. any ideas?
thanks.

[factor-fiction]

may just be the internal fan cooling it down

[ACtheTROLL]

you don't say which OS ... but XP and vista both do "housekeeping" when they detect idle time. .... and depending on your set up automatic updates will run.
as (possibly) will other apps

and assuming you have a virus scanner ... that will do it's thing also.

then again ... you could have a nasty sending e-mails spam ... defrauding financial institutions ....

google spybot search and destroy, ad-aware ... and scan your machine .....
also make shure your virus scanner (you do have one??)
is up to date ... and use it

[KARL]

My first thought would be a failing fan - the bearings may be varying in friction. If your computer has had a lot of use (whether old or not so old), for example if it is left on rather than switched off when not working, then this is a likely explanation. Usually most of the sound from a computer comes from fans (power supply, CPU cooler, system/case fan(s)), not from hard drives although they do make a noise just lower in volume.

[ACtheTROLL]

but the fan isn't going to run the HDD ... nor should it use any processor time at all

if it;s just fan noise ... ok ... but that won't cause the cpu to hit 40% .... (it could well cause it to shutdown) ...
and whatever else again ... the HDD shouldn't be affected