The Low Drone
About a month ago, whenever I turned my computer on, I noticed this loud humming emanating from the tower - louder than it usually is anyway - which I was pretty sure was coming from the power supply fan at the back of the case, a loose bearing or something like that. The noise went away after a few seconds anyway during bootup, so it didn't really worry me all that much. And then, a few weeks after that, the noise stopped altogether and so I forgot all about it.
I little while ago however, I'd just about had enough of all the fans constantly whirring away inside my case, making all kinds of noises all throughout the night, so I decided I didn't really need all those case fans anyway and my system could probably still survive without some of them and then I would be able to keep my sanity as well. As it turns out, it was a good think I opened up the case to disconnect three of my case fans, because while I was at it, I checked on the graphics card fan and found that it was just about jammed in place and obviously hadn't been spinning for quite some time.
Then it became clear, that the noise I had been hearing all that time ago, wasn't the power supply fan at all, but was my graphics card fan on its last legs all along. One of my friends' video card chipsets was cooked not long ago, all because a fan stopped working, so I was just relieved to see that my card was still functioning properly and had survived the heat. I managed to pull the fan apart and after a lot of fiddling around, half got it going again. But now, every so often, it will start to make that horrible low droning buzz, reminding me that a new fan is in order.