Premium to Ultimate Upgrade problem

So, I've been trying to find a good explanation, but everything I've
found says I shouldn't be having a problem.

I bought a new computer with Premium x64. Awhile back I had been able
to purchase a copy of Ultimate from the Microsoft Employee Store through
my employer.

After getting the computer cleaned of bloatware and installed with my
copies of Office and other programs, I realized Premium didn't have
remote access enabled, so I tossed the Ultimate disc in.

I did this while in Windows, not on boot. As others have had problems
with, the upgrade option is disabled.

Am I missing something to be able to do the upgrade?