How to install a Vista upgrade on any PC
Unadvertised sale: Buy an upgrade, get a stand-alone version
Microsoft is running an unadvertised sale on Windows Vista. For the price of an upgrade edition requiring an existing copy of Windows, anyone can have a stand-alone version of Vista that will run on any PC. Indeed, the upgrade editions are full versions, simply waiting to be told to install themselves regardless of what OS is currently on the system, if any. The trick is all in how you interact with the setup program.
Microsoft MVP Marc Liron was kind enough to explain the procedure in this recent article, and we merely set about duplicating his results. Which we did, with an upgrade version of Vista Home Premium, and found that Liron's instructions worked like a charm.
In short, all you need to do is delay entering your product key and delay validating your copy of Vista online until the setup is complete. For some reason, Microsoft has decided to allow users to install first and deal with the paperwork later. Simple in theory, although the details of exactly how to do this are a bit lengthy, and we strongly recommend following Liron's step-by-step instructions linked above. But, in a nutshell, all you are doing is avoiding the traps that MS has set up to cancel the installation if an authorised version of Windows isn't already present. If you dodge those traps, you can install a stand-alone version of Vista, using an upgrade package, on any machine, and later enter your product key and validate your copy normally.
We took a PC with a valid copy of Windows XP, and nuked the XP image (always a satisfying experience for a Linux user). Then we booted from the Vista upgrade DVD, and, following Liron's instructions, got ourselves a fully operable and properly validated copy of Vista in about an hour's time, without a single misstep (again, we've confirmed this with the Home Premium upgrade only, but we have no reason to believe that the trick would not work with other editions).
So, for those of you still using Windows 98 or the ludicrous ME, or Linux, Vista just got a good deal cheaper. Would this technique also work on an Intel-powered Mac? I have no idea, but I'd guess that if you know how to re-partition your disks, and so long as there's nothing truly weird in the EFI, it ought to work. And the rEFIt Project might be able to offer assistance to anyone willing to experiment (I don't do Macs, so I'm not a candidate).
No doubt readers are wondering why Microsoft designed the Vista upgrades to be so easily installed as a free-standing OS. I'd like to answer this question, but I have nothing more than a clue. But it's an interesting clue.
I had a Windows XP Professional image on one of my computers. Now, the Vista Update Advisor recommended that I upgrade to Vista Business, but I didn't wish to. I went to the shop, looked about, and decided on the Home Premium upgrade. According to the package, Home Premium can be used on the following Windows OS's: "Windows 2000 Professional, Windows XP, or Windows Vista." That's a quote.