I believe that you can download the Mcafee file on their website, provided you have your license key and or mcafee account username and password. The last time I installed, I just logged in, downloaded it, installed, and no key was necessary! I now use NOD32, but I doubt it has changed in the last couple of months...
(P.S. Mcafee is a pretty good paid anti-virus, but NOD32 can catch alot more than mcafee, heck if I even TRY to download a virus, NOD32 stops it before it even finishes. That's what I call a good AV, and lightweight too!)
Most your programs store information in the registry,
you'll need to reinstall things like Office 2007, McAfee etc..
with most programs (both of those, luckily) you get 3 licenses, so you can install both again on that partition.