Vista Horizons

Be very careful which version you buy. If, like me, you like to do a clean install of your computer when ever you do an OS upgrade you will NOT  be able to if you bought the Upgrade disk.
MS KB# 930985: Windows Vista does not check upgrade compliance. Therefore, you cannot use an upgrade key to perform a clean installation of Windows Vista.
You can:
* Upgrade to Windows Vista from an earlier, supported version of Windows that is already installed on the computer.
OR
* Purchase a license that lets you perform a clean installation of Windows Vista.
(More from arsechnica)

If you bought the upgrade disk and want to get as close to a clean install as possible, hopefully have have a Ghost image of your basic setup then you can do an upgrade. Alternatively, if you  have the restore disks if you bought your computer from a major brand like HP, Dell or Sony, you could do that first and then the install.
You'll have to decide for yourself and weigh the cost of your time relative to the $70 or $80 cost difference between a Full or Upgrade DVD.

Here is my handy chart again:
A Yes indicates an in place upgrade is possible. A No indicates you'll need to do a fresh install.

Tags: microsoft, windows, vista, upgrade, guide, caveat