Meh--I used to use "normal" isopropyl alcohol--but it was 70%. Lemme tell ya--using that to clean was a real b***h. I've not used anything higher-purity, though with my last build (Dec '07) I decided to get some Arctic Silver ArctiClean. Easy to use stuff--plenty of it too. Cleans like a charm. On NewEgg it was only $6 or so. I used primarily paper towels actually--they're handy. I usually covered the heatsink or processor with each part, soaked for anywhere from 30 seconds to 30 minutes (depending on what I was doing), and then wiped it all off by a single swipe of the paper towel. After that there's a surface purifier that seems to work pretty well.