For testing purposes only, I installed Windows 8 with Media Center without a key and activated with MTK 2.5 B5. Then I launched Setup to upgrade to Windows 8.1 with Media center. But upgrade stopped after getting the following Message: "Setup has failed to validate product key". Exists a workaround to solve this problem ?
What key did you enter in the setup? and do note, ProWMC activated with MTK become Volume Edition, not retail