But with Vista, Microsoft seems to have confused itself, creating a loophole for customers with a do-it-yourself bent to save as much as $140 per copy of Vista.

On Friday, Microsoft confirmed since the beginning of the month that customers can successfully install an upgrade version of Vista on a computer without Windows XP or 2000 already on it, through a bit of installation ledgerdemain.

Here's how the works according to :

--Boot with the Windows Vista upgrade DVD and begin the full installation process.

--Do not enter the product key when prompted, but continue on.