You all know that any Vista Upgrade will ONLY allow you to install within a qualified previous version of windows. No direct booting allowed.
Well I recently found out today that you can get the upgrade and decline to enter the CD key. Install basic, and of course you will get declined on the activation.
Well try running the Vista Installation within your 30-day limited copy and you will be able to install Vista without having to install an older OS. Therefor you are saving yourself a good chunk of money by not buying the full version.
I have tried this method and it does work.