I have vista ultimate on my computers, it would not install because I have all the language packs installed. Why you might ask do I have them installed? Well it is just one of those things of just checkin everything and hitting install and letting the computer run overnight. This was when vista first came out. Now I just hide them all so people do not know they are missing stuff.
It turns out it is a real pain to get rid of the language packs. I did it on one computer, it is a reboot cycle for each language pack. You cannot remove them all at once, it will only remove the first one then decide it cannot remove more since the files all need to be updated again so it wants you to reboot between each one.