Concerning Windows Vista "Upgrades"
For the first time in history, upgrading from a previous release of Windows (Windows XP) to Windows Vista (any edition) actually "works". I found this to be true, but honestly didn't trust it 100% since history has shown me that this was a bad idea. However, according to someone in the know, the way Windows Vista "upgrades" is a little bit different. It doesn't actually upgrade per say, but rather creates an inventory of information, wipes the existing installation, does the new installation and, using the inventory of information, "restores" the old stuff to the new installation. For a full rundown on how this works,
go here.