Change Windows 8.1 Pro w/ Mediacenter install key before Windows 10 upgrade?

[sprtfan]

My main computer has retail Windows 8.1 Pro w/ Mediacenter installed. I decided to move this license to a 2nd HTPC before doing the Windows 10 upgrade since I'd lose Mediacenter when I do. I have another Windows 8.1 Pro license I can use in its place. I tried to change it, but get a message that I can't use that code for the installed version of Windows. I'm assuming its because one has Mediacenter and one doesn't. Anyone know if I uninstall Mediacenter will it let me switch? or would the only option be to do a clean install of Windows 10 on my main computer and use the other Windows 8 pro license at that point? (I haven't done a clean install with Windows 10 yet but I assume it will prompt for either a Windows 7 or Windows 8 license at some point during the install). Thanks for the help.