Go to your local computer store, BestBuy, CompUSA, CircuitCity, or anyplace that sells electronics for that matter, and buy a can of compressed air.
This is the safest way for cleaning out all of that dust. However, it does make a big mess (stirring the dust in the air). Anyway, just spray the dust off your computer parts, and if you notice a little frost buildup on some parts don't worry it evaporates quickly.