Yeah that is what I am going to have to do. I have to buy the full version that is 300 dollars since my Vista came pre installed, darn another 300 to use the iphone, oh well. That is what I get for going 64 bit
DL the free MS Virtual Desktkop or Virtual server, install vista 32 bit with no key its a 30 day trial. then use that guest os to make it work. the net has a command to reset the 30 day trial 3 times to last 90 days.
if your vista 64 is a driver issue, there is a boot.ini switch you can add to allow unsigned drivers.
Since you're only going to use it for activation and subsequent synching, you could go with Windows XP. Might be less hassle.
What would be sweet is if in Parallels you can access your host drive, then you could get your data (movies, songs, TV shows, etc) prep'd in Vista and then just launch XP to sync.
Regarding using a non activated version of Vista, remember you need to use iTunes every time you want to add / remove files. I would not recommend that method, even though it would work for activation.