I know this is an old thread but - just having had the same issues, thought I'd be clear with everyone on the answer. Do your Windows Update! I got a little anxious with a new install of Windows 7 and MediaPortal - a bit too anxious as I installed MediaPortal before I completed the current Windows Updates. I did the update - still didn't work. Uninstalled MediaPortal, Reinstalled MediaPortal - and voila! Victory!