I just replaced my Vertex 4 with an 840 Pro and now Windows 8 isn't activating. Normally I'm good at this stuff but I'm almost at my wits end. I have a legitimate copy of Windows 8 Pro upgraded to Windows 8 Pro with Media Center. I have tried both keys to activate. My Windows 8 Pro key just says that I need a MCE key. When I use my MCE key it just says that I can't use it because it is an upgrade key on a retail install. I have tried changing the MediaBootInstall key in OOBE and rearming but when trying to rearm it just says that I can't use that on a "non-core" version of Windows 8. Any help would be greatly appreciated.