why you might not need to buy a full version of Vista

The guys at Microsoft changed the upgrade process in Vista. In old good times, when you for instance upgraded from win95 to win 98, you didn't necessarily have to launch the upgrade from inside 95. You could boot your upgrade CD, and when prompted insert the old version CD, and enter the old key. NOT WITH VISTA! These bastards want to force you to launch the Vista upgrade from inside XP ,that means first install XP, activate it, then insert and launch the Vista CD, and have the choice between an upgrade process (the worse), or a pseudo-clean install that will put all your old xp files into a folder called windows old, with possible rollback. Whatever your choice is, the install won't be clean at all. You won't be able to format and install directly from the Vista CD. Disgusting!
Now some guys found this:

1. "Boot from the Windows Vista Upgrade DVD and start the setup program.
   
2. When prompted to enter your product key, DO NOT enter it. Click "Next" and proceed with setup. This will install Windows Vista as a 30-day trial.
   
3. When prompted, select the edition of Vista which you have purchased and continue with setup.
   
4. Once setup has been completed and you have been brought to the desktop for the first time, run the install program from within Windows Vista.
   
5. This time, type in your product key when prompted.
   
6. When asked whether to perform an Upgrade or Custom (advanced) install, choose Custom (advanced) to perform a clean install of Vista. Yes, this means that you will have to install Vista for a second time.
   
7. Once setup has completed for the second time, you should be able to activate Windows Vista normally. You can also delete the Windows.old directory which contains information from the first Vista install.
   

There's no telling why Microsoft left this loophole wide open with Windows Vista Upgrade DVDs, but this means that any retail upgrade DVD can be used as a fully functioning full retail copy of Vista."

I can imagine why, they just didn't have the choice, as any windows Vista DVD must remain bootable for repair purposes or else, you can naturally boot with an upgrade DVD, and upgrade your install with a new "clean" install" of Vista itself. Well they actually could have prevented the install with no key, that leads to a 30 days trial version, and miss an opportunity to make buy a new license after install, just in case you would like to upgrade you initial key from Home Basic to Premium for instance. That's ridiculous. My conclusion is that anyone wanting to perform a real clean install of Windows Vista should unfortunately buy the full retail version, and avoid the upgrade!

ps. well they could have forced the user to enter a key when booting from CD, and then block the install in case of an upgrade version.But they left it open the way it is open when you boot from a full version, or the way it is open when you launch the upgrade normally, from XP. I wonder what happens when after a no key install, you enter it from inside Vista...probably no possible activation, or no entering of a new key if the product is not already activated...I don't care really. Once again, 2 obvious choices: OEM, or FULL!