A clear inch of dust!
Cleaned out my room a month or so ago, and up against the window-sill I had a stack of PC User magazines (heresy, I know).
They must have been there a while, because as soon as I removed them I noticed a clear and distinct line of dust where the edge of the magazines once sat. Scary stuff – needless to say, my room is now pretty clean. Actually, scratch that; a set of 4.1 Logitech speakers (no I didnt lose a speaker, they’re branded as 4.1), and a gigabit PCI network card that I bought of PC Case Gear because I thought the gigabit ports on my motherboard were stuffed. Turns out they weren’t – some residual power issue was running rampant, and leaving my PC unplugged for a while seems to have fixed the issue. /shrugs.