Sorry if this isn't what you wanted to hear, but you are going to need to do a Format C: I take it one step further and then delete the partition completely after that.

Don't even think about trying to just file copy your old 32 bit programs into a next generation 64 bit OS. It won't work most of the time anyway, since they need to be installed into the registry.

Just wipe it. You'll be surprised how quickly it actually goes. And all of your programs will have nice clean installs. The only thing that matters is your personal files (doc's, pictures, etc). Everything else can be reinstalled much faster than you think. (Including your WoW addins).