Whirring Sound?

[CiscoJP]

Last night I went to download the update for WoW. Anyway, my hard drive and fan seemed to be spinning very high. Towards the end of the download, I heard a "whirring" or "whistling" sound, which sort of faded in, got a little loud, and then faded out. It did it about 3 different times, but hasn't done it since. Is this an indication that something is wrong with my hard drive? Or could it have been the cooling fan? My first hard drive that crashed would give me a clicking sound, but this was a high-pitched whirr or whistle. Any ideas?

 

[XFlamez]

put your hands near the fan when its on, does it feel really hot or just warm?
if its really hot, then its the fan or heatsink

i wouldn't think its the hard drive making that sound, but i could be wrong.
is the side case screwed on tightly?

 

[Nitestick]

you weren't using a cd/dvd drive at the time? a hdd unless its really screwed up would either make a clicking noise or a constant whirring noise, it wouldn't fluctuate. sound's like a fan, if you can get a monitor for the rpm of your fans you could see if it fluctuates when you hear the noise.