I ran in to a problem not long ago where I was trying to uninstall 3dsmax and a couple other programs and for what ever reason they kept erroring and were not able to uninstall, I found a killer little M$ utility that actually works awesome for programs that wont uninstall and thought I would share as this thing is pretty awesome. Ive used it already on a couple render slaves and workstations and has worked flawlessly.
Check it out here: Fix problems that block programs from being installed or removed - Microsoft Support
Cheers,
-dave