Even though the support wizards at Zune told me it wasn't compatible, I had a hunch it had more to do with me trying to install the previous version of ZuneSetup (the one that wasn't Windows Vista compatible) than the version of Vista I was using. Sure enough, in the comments and through my own confirmation I found this to be false. I re-imaged my laptop with a fresh install of Windows Vista Enterprise and ZuneSetup 1.2.5511.0 installed like a champ. My only complaint now is that I cannot authenticate...