Fujek: Wouldn't all of the four points you mentioned be rather strange, given that the computer has been running for at least two years now, without any change of hardware, or even opening the case?
TVs_Frank: Remember that your computer is a hot environment. Plastics expand, metals expand, and nobody has yet to come up with a solution for... crap, I forgot what was the name for the thing where the metal over time forms little... tendrils and eventually creates a short by meeting another metal it wasn't supposed to.
It's called fatigue. It's caused by periodic stress of some sort, and results in structural detoriating and, eventually, failure. Short-circuits are one possible result of that.
And Fujek, I'd recommend opening the case and cleaning it of dust if it's been going for two years now. Buy some pressurised air, unplug all the wires from your case, open it, ground yourself and blow the dust away, especially from heatsinks. Having a vacuum cleaner nearby could be useful (otherwise the escaped dust will be all over the place), but don't stick it inside the case; this can result in a static electricity discharge which would ruin something or other.
