What's this (computer) noise?

Factual Questions
1

Frequently I get this whirring noise from my desktop PC. I figure it’s not a good thing so I restart it and it will go away. Unless I am mistaken, there are only two mechanical things inside a computer that make noise…the fan and the hard drive when spinning. I know it’s not the fan so my educated guess is that it’s the hard drive.

Assuming I am correct, why would this happen, how do I fix it and how concerned should I be?

Thanks.

2

There is also the CPU fan. Those can be noisy too.

Every once in a while, you’ll find a CD or DVD drive that resonates with something else.

3

Speedfan will tell you how fast your fans are running and temps of your CPU, motherboard and video card. Something might be overheating and you’re hearing the fan(s) speeding up.

4

There’s also a fan on some graphics cards.

Whirring noises could mean that a bearing is going out in one of these many spinning things (CPU fan, case fan, graphics card fan, disk drive). If it really is the disk drive, well, make good backups. It may run for years with the bearing going south or it may die tomorrow. If it’s a fan bearing going, replace the fan.

That said, it may just be that you’ve got a fan or two kicking on from heat, and this fan just happens to be naturally a bit noisier than the others. Your CPU fan may be of the variable speed type, and the whirring may just be that it’s working really hard because your CPU is getting hot. The graphics card fan may only kick on when the temperature of the graphics chip reaches a certain level. Reboot and give things a chance to cool and there’s no reason for the fans to kick onto high level. So, it’s possible that what you are hearing is normal.

So, it’s either a sign of impending doom or everything is fine.

5

There can also be a fan in the PSU.

6

I notice that nobody has yet suggested demons.
You should never discount the power of the darkside.

But it is probably a imbalanced fan. Try cleaning your fans with some compressed air.
If that doesn’t work, sacrifice a chicken.

7

Or a virgin.

If you can find one.

8

My computers’ fans have always begun making noise when they get too dusty. I guess it throws them a bit off balance. Blowing or vacuuming them out fixes it.

9

You read his user name, right? Good luck with that…