Anytime Upgrade from Scratch?

[Guest]

I got a business version from my school, and installed it onto a 2nd
partition (XP MCE is on the first). I would like to have ultimate, and to
upgrade my MCE partition to ultimate, but I want to do an in-place upgrade,
but you can't do an in-place upgrade from XP media center to business, only
to home premium or ultimate. If I buy the anytime upgrade to ultimate on my
Vista partition, can I then use that to upgrade in place XP to ultimate?
Will it give me a new key to unlock that edition directly during the instal?

 

[Guest]

To be clear, I'm asking if I get a new license key that effectively replaces
my old one, and unlocks the full Ultimate version on the disc so i can
install straight from a format or XP to Ultimate (since all discs are the
same), or if i will forever have to install business first then download the
software that allows the update?