Are you like most everyone that figured, "Hey, just like windows xp/vista/7, when a new version of the "same" os comes out, i'll still be able to use the same CD key to install directly from the newer ISO/DVD itself." Example being: Have an original Windows 7 key, But install fresh/from scratch using a Windows 7 SP1 disk. OR Have a windows Vista key, but install freshly from vista SP2 Disk. WELL Boys and girls, if you were expecting to install 8.1 fresh using your existing 8.0 key, you're out of luck as the key is unrecognized and considers them all invalid. I'm currently checking to see if installing 8.1 fresh using the provided 8.1 key, and then "changing it" when I get into windows 8.1 back to the systems original 8.0 key. This is kinda fucked up imo. Just be warned, not entirely sure about pre-installed keys on existing laptops/desktops however.