Now forcing a third party codec to play natively supported codecs isn't going to be easy, but it is possible. Hack7MC.com has a pretty good explanation of just how to get it done.

They have managed to disable the Microsoft DTV/DVD Decoder so you can use FFDShow, with suitable codecs.

Here you can find the guide about disabling the Microsoft DTV/DVD Decoder.

And last but not least Hack7MC.com did also publish "MKVs for Minimalists on Windows 7". You can find this excellent guide here.