I once had a cellophane sweet wrapper slip under my case and the fan intake made it rub against the filter, so I'd have this high-pitched scraping noise going on.
Saw an nVidia FX 5600 in an electronics shop this afternoon for 49.99 euros. Before you get excited, it was the AGP card, not the Quaddro. Why would something like that be 50 euros (80 dollars)? Belongs in a museum. Of course, this is a store whose sound-card selection amounts to two Creative Labs cards, and a noname brand card with one (that's right, one) capacitor and two chips on the PCB, but still.