zackbass

For future reference if you ever need to remove a thermal pad the way I usually do it is by first scraping it off with a credit card or razor blade, and then using your favorite solvent to get the rest. The residue from the pads can be prety bad and may require something more heavy duty than Isopropyl Alcohol, perhaps Carb cleaner from the auto parts store. Just remember to do a final wipe with the Isopropyl and a lint free cloth (coffee filters work well) to pick up anything that may have been left behind during the heavy duty cleaning.

AstroCreep

I just use 90% I.A., but I know a lot of people use 'Goof-Off' too...
Not 'Goo-Gone', however, as it is citrus-based; being acidic if a little was left on the CPU die/heatspreader, it could cause some problems for the fresh thermal-transfer-material.

Triumphrider

Carb cleaner is generally bad for electrical/electronic stuff- it's got a light oil in it, intended to lubricate the carb linkages. Brake cleaner evaporates clean, as does electric motor cleaner (brake cleaner is generally cheaper and I've never ruined anything with it). Lacquer thinner has a small amount of water in it, no issue on some stuff but might be an issue with electronics.

Old fashioned nail polish remover is straight acetone, fairly cheap in small quantities and good for the task at hand.

Another sometimes useful solvent is gasoline- I've got a friend who thins oil-based paint with it, surprisingly it seems to work well.