That me be true for Windows Media Player or MPC-HC, however FFDShow and Avisynth won't work with Windows 7 "Media Center" because the Media Center requires the x64 versions to work. I have managed to get the x64 FFDShow working with Media Center however the scripts don't work with the x64 version of Avisyth.
You must use an external player like Zoom Player or MPC-HC x86 (MPC-HC x64 doesn't work)
As front-end you can use Media Portal + Moving Pictures and External Player or Media Center + Media Media Browser and External Player.
My system is only W7 x64!
and run with:
avsynth (upscaling and doubling frame rate scripts)