computer sounds

my computer is on the older side. and mostly hand me downs from my brother as he upgraded his own computer. Lately when I turn it on it makes a ungodly screech from the fans as it warms up. once it gets warmed up and going the noise stops, or at least the horrible "scrooong" noise shifts up out of the range of human hearing. The parts on the computer are old enough to Blame Bush, and Thank Obama so the fact that it still runs at all should be more of a surprise than that it just makes some strange noises as it starts up. I keep thinking I'm going to save up to buy a new computer, but then I spend too much money on food.