I was surprised when I received an email asking the question about whether to do an upgrade or clean install of Vista over XP. The answer is simple. The next time you get the oil changed in your car tell the mechanic to only drain out 3 quarts and leave 2 dirty quarts in the oil pan. The sames go for a upgrade. All you do is leave ‘dirty oil’ behind after you do the install.

Yes it is time consuming to backup your stuff, install the operating system and reinstall your programs. But if you do a clean install your computer will thank you and you should have less issues, i.e. left over junk and gunk left behind.

You should be aware that the upgrade DVD for Vista no longer does a verification check for a copy of an older version of Windows. So you can do a clean install with an upgrade disk. You also have the option to use a System Builder DVD to save a few bucks as well. Just beware that using a System Builder DVD does not include any support from Microsoft.  You in fact become your own support for the installation.

I have been using Windows since Windows was in diapers. I have yet to call Microsoft for support. The only time I have called Redmond is when I encountered a problem with a product key.

Comments welcome.

Source - Installing Upgrade DVD As Full Version.