After a hardware change, Windows Media Center (WMC) will probably start to display "Video playback device does not support playback of protected content" when watching protected content (e.g. CableCARD). This isn't a HDCP issue, it's your PlayReady DRM keys.
As an Administrator:
- Close Windows Media Center (and turn off any Windows Media Center Extenders)
- File Explorer | Options - Select "Show hidden file, folders, and drives"
- File Explorer | Options - Uncheck "Hide protected operating system files"
- File Explorer - rename these (e.g. Cache --> Cache.old)
- Download ResetDRM.exe from the Microsoft Download Center (http://go.microsoft.com/fwlink?LinkId=105000)
- Extract the EXE using WinRAR (etc)
- You need to use WinRAR to do the extraction because the EXE's self-extraction only supports Windows XP
- Open an Administrator Command Prompt (Win+X, A)
- Run "CleanDRM.exe -v"
- Open Windows Media Center
- Update PlayReady via "Settings | TV | TV Signal | Update PlayReady"
- (Revert) File Explorer | Options - Select "Show hidden file, folders, and drives"
- (Revert) File Explorer | Options - Uncheck "Hide protected operating system files"
Note, this isn't an official Microsoft solution. It's what I cobbled together from multiple posts on this issue.