What is the proof requirement for Upgrade versions of Vista? XP or 2000 needs to be installed. Regarding whether or not a "clean" installation is possible, the answer is a resounding maybe -- it's not always up to you. Vista requires a clean install in some cases, depending on which Upgrade version of Vista you're installing, and which version of Windows you're upgrading from (Again, see our for specifics).

I've said it before, and I'll say it again: . But if you really must, consider only two of the 10 versions: Nontechnical consumers should buy the full version of Windows Vista Home Premium, and power users should buy the full version of Windows Vista Ultimate.

(Windows Vista Starter Edition is for Third World countries. The Enterprise Edition is for big companies. The Business Edition doesn't have any of the cool multimedia stuff you want from Vista. Home Basic versions are crippled. The Upgrade versions are poison.)

Here's what you need to know about actually performing the installation of Windows Vista in Hands On: .

It's obvious that Microsoft decided to extract maximum cash from consumers by micro-segmenting the market and trying to provide a different version for each. But they may end up with the opposite result. All this confusion over versions and upgrade policies will motivate unknown millions of consumers to simply stick with Windows XP or move to a Mac.