clean install of vista with an upgrade dvd?

I purchased a downloaded copy of vista today, and was having some issues with
installation process. After the 1st restart it would come to what I would
assume is the Vista Logo screen sans the Vista Logo, and then it would just
stay there. I would then restart the PC, and boot into the previous version
of Windows, which in my case is XP Media Center Edition. After some browsing
of the boards here, I have seen many posts regarding the clean install of
Vista with only the upgrade version. Am I correct in understanding that all
I have to do is skip the activation key page, and choose clean install? I
have also seen a few posts that state you have to go back and do a upgrade
over the clean install for the activation key to work. Is this true? I have
gone back and updated all of my drivers to Vista compatible ones (the ones
that will let me do it with XP installed anyway) and uninstall Norton 360
(which I can't figure out how to disable), and then try the upgrade path to
see if that works first, but if I have to I would like to try the clean
install if its possible. Thanks for your input,
Todd