Go to Control Panel > Programs and Features. Onthe left pane, click on "Turn Windows features on or off". In that window that pops up, expand Media Features, then uncheck the Windows Media Center. Click Yes in the popup that appears, then click OK. When it is done uninstalling, go ahead and reboot to make sure it clears anything out, then go back into that same screen and check teh box for Windows Media Center to re-add it. I have had that fix several issues with WMC.