Microsoft's US Senior Manager in charge of Small Business Community Engagement Eric Ligman published a post on Friday outlining, in what he regards as very simple terms, the fact that to upgrade to Windows Vista you must have something there to upgrade from! The article can be found here but I've quoted a couple of paragraphs below,
It seems that there are some people out there who don’t quite get the concept of an upgrade. Some have even written articles fully articulating how little they know. Because of this, I am going to explain it again and even use pictures to try to make this very simple…
You can buy a software full license that gets you the rights to install and run the software. You can buy a software upgrade license that allows you to upgrade from the full license you have to the upgraded product you purchased the upgrade for.
So if you see anyone stating, or writing, that buying an upgrade by itself (Windows Vista Upgrade for instance) without having a full license first gets you the rights to run the software, just realize that what the person is actually stating is, “I clearly have no clue what I am talking about and so I am writing a bunch of gibberish that proves this hoping people will think I have a clue, even though I obviously don’t.”
The post is worth reading but it basically states what we should all already know. If you're going to buy an upgrade version of Vista then you must have an earlier, fully licensed, product installed to upgrade from. And for those buying OEM copies remember that they are meant for registered OEM vendors who are reselling the computer they are building, not for the average user on the street. For everyone else you have to buy a full copy of Vista. It's that simple.