Cannot perform upgrade from win 7 Home Prem to Win 7 Pro

Issue is on my laptop which is an HP. It is currently running Windows 7 Home Premium x64 HP OEM. I have a valid copy of Windows 7 Professional x64 but whenever I try doing an upgrade it tells me to use Anytime Upgrade, which will not work with my serial key.

I would rather not do a full install if possible, and am curious why I cannot perform this upgrade?

Any comments or suggestions would be helpful.

BTW My Win 7 Pro license is an MSDN AA key from my school, never activated and legit.

Your spec's show that you have three OS's already installed.

Windows 7 HP x64
Windows 7 Pro x32
Windows 7 Pro x64

sorry no on the laptop only win 7 home prem, the others are the editions I have available

Are you typing in right key No.
B & 8, 0 & o, Q & O

No install files needed.
Only the Upgrade key is neeed.
Anytime upgrade only adds-on the Programs & Features from version to version.
Windows Anytime Upgrade - How to

If Anytime will proceed with upgrade HP>Pro then it should accept a retail key. Try again.

If not, there is a workaround to change between versions of Win7 using an in-place Upgrade from disk. Question on updating from home premium to pro

hey thanks greg, found that out right before you posted, worked like a charm. Now running my Win 7 Pro x64.

Thanks to all who replied in trying to help!

Which worked: inserting retail key in Anytime, or doing the reg workaround to change versions in-place via Repair Install?