Just a note: Gaara's description of how to apply thermal compound (AS5 at least, which is the best one to use anyway) is EXACTLY correct...straight off the arctic silver website, as linked by An0nym0us. They do not recommend spreading the compound out (you were supposed to spread it with their older compounds, but not AS5). Wipe off old compound with high purity rubbing alcohol, xylene, or acetone (NOT acetone-based nail polishes, they have other crap in it). Clean it off with something that is lint-free, arctic silver recommends a coffee filter. Follow their instructions, they know best.
Sorry if I'm beating a dead horse here, just don't want this guy to get led down the wrong path.