I'd just like to know if it's possible to reuse an OEM Windows 8 key on the same PC after reformatting the drive. Would the key only work with Windows 8 an installation or will it work with 8.1? I know 8.1 is a free upgrade if you have 8, but I need confirmation so I know whether to install 8 or 8.1. The PC came with Windows 8 with a key.