I upgrade my Surface Pro from OEM win8.0 to win8.1 through the store. It ask me to enter key for activation. I don't have the original key. It only showed last 5 letters of the OEM key on my Win8.0. I thought the upgrade should automatically take my OEM key, but did not. It says the current key does not work and need a new key. I contact Microsoft, and after asking many questions, I was told they need 2-3 days to respond. I wonder if anyone else had the same issue?