|AMD recommends a pad only. I usually use the pad for the initial install, then if I remove the HSF for some reason, I go with paste. I use Radio Shack paste too. It sells for about $2 a tube & works damn near as good as the high priced stuff, but I'm sure many will sing the praises of Arctic Silver.|
Scrape the old pad off with a non-metal object - the edge of a credit card or something similar works well. Clean off the residue with some sort of solvent that doesn't leave a residue of it's own behind. Goofoff works well, so does lacquer thinner, acetone, or alcohol (100% if you can find it). Once it's clean, do NOT touch the bottom of the heatsink or the CPU core - dirt, skin oil, fingerprints, etc can contaminate the surface & reduce thermal transfer.
Arctic Silver has excellent instructions. Follow them no matter which brand of paste you use: