(EDIT: SOLVED) I'm trying to install en_windows_8_1_x64_dvd_2707217.iso with the "default" key ending in C9WBK and I get this error, before it even starts installing. I checked the key, it's definitely correct. Searching I found some people with the same problem and the cause was their existing Win7 install, but it looks like they were doing an upgrade. Anyway, the solution to fix it with a registry tweak doesn't apply to me, since the registry is already as it should be. I currently have Win 7 Ultimate on this PC (Daz loader), but I doubt the installer actually cares about that, or does it? I'll do a clean install, but as I said the error comes up before the install even starts.