I have attempted to create a Windows 8.1 with Media Center x64 but having no luck. I have tried various WIM's and keep running into problems. Has anyone had success creating one?
Follow the post in "Windows 8.1 Activation (Current Known Method)" I was successful in adding WMC feature to Windows 8.1 Pro x64 and eventually activating it using the Free WMC producy key provided by MS last year. What errors are you getting?