A recent success story from a reader, who solved a problem with his PC crashing by replacing his system memory , reminded me that gold and tin don't mix . Most users who do not routinely clean out their cases will find a similar colony of dust bunnies when they eventually do open them up.
Excessive dust can also lead to cooling fans locking up.
Work it in, and the fan may start working again. Failing that, be sure to replace any fan that stops working promptly. This surprises some people. In particular, buying the absolutely fastest CPU on the market is almost always a waste of money. In the real world, most people would notice no difference between the chips.