failure to upgrade from media center XP to vista business edition

Hi:

I bought vista business because upgrade advisor showed no problem
upgrading from media center XP to vista business edition. when I was
installing it, however, it says no upgrade available for media center XP to
vista business edition(I absolutely don't want to install business on another
drive or partition because then all the Manuafacturer softwares and drivers
won't be able to be installed on business); it can be only upgraded to
ultimate or home edition. Now if i want to install vista at all, do i need to
buy a new ultimate or buy upgrade from business to ultimate? I really need
help please.
Thanks
Yujiao