Each license grants you the right to install a single copy on a single machine, so you technically have to purchase two licenses even if they are both for the same machine and will never be used at the same time.
John
I'm planning to use my HTPC for Games, but I dont want the games to mess up the media center side of my HTPC. I want to create a partition and install windows vista on both partitions. Would I need to purchase two seperate licenses for windows Vista or will the one license do?

Chowhound
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