I'm using Vista Enterprise with a KMS server and Deepfreeze but had to jump through a few hoops to get everything working. There is an alternative to sysprepping every machine; use slmgr.vbs to change the CMID. You can use the Ghost console to push it out to the clients so that they will authorize with the KMS. If anyone needs details I can provide them. The newest version of Deepfreeze seems to work okay too.