Whirring sound...my fan?

I'm hearing a whirring sound coming from my computer. It speeds up and slows down, but starts only after my computer has been on for a few minutes. If I sort of rock the casing and let the computer bang gently on my desk, the sound stops briefly (figured this out accidentally, I'm not the type to beat my computer). I doubt it's the hard drive, since I har no clicking or anything like that, and my computer has suffered no slowdown. Does this sound like it could be my fan? if so, is there an easy fix for this? Thanks.

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yeh sounds like a fan, open up the case when its making the noise and listen to where its coming from. It normally means that the bearings are going, there isnt really a fix for that, you basically just have to get a new fan or suffer the noise.

Ok I checked it out, and it seems like it's coming not from the fan in the back of the case, but the fan on the motherboard(?) blowing out the side. I used a can of air cleaner to get the dust out, and that seems to have helped a little, but it still makes noise. If it is the bearings, how long can I safely continue to use the fan, if I can't replace it right away? And is it an easy fix? I'm no expert, but I've upgraded RAM before, swapped out video cards, etc. I'm just not familiar with fans at all. Thanks for the help.

If it's helped I guess it'll be Ok, fans will never be completely silent, so I wouldn't worry too much. If you stop hearing it and discover the fan has stopped, then I'd replace it, but for now, I wouldn't worry