how to reset ONLY product key?

[mikegillow]

I'm trying to build a vmware vm that is completely preconfigured (users, applications, drive letters of partitions, etc) and have an end-user have to supply ONLY their Vista Business product key when they try to use it for the first time. This project is a 'sandbox' VM with our product preinstalled and ready to run. So the concept is simple - do something to make Vista request a different product key, but change nothing else. But I'm finding that implemetation of the concept is a lot harder than I expected and I could use some help.

What sysprep options do I use? I assume I must use generalize to trigger the requirement for new product key.

What components do I need to add to an answer file to eaither leave things the way they were or put them back? (one of my problems is the drive letter for a partition being changed)

thanks

[mikegillow]

perhaps I'm going about this all wrong... I've been so used to sysprep with XP that my searching kept missing "slmgr -upk" for Vista. If that doesn't do the trick for me, I'll be back...