This should be of interest to Digital Media fans. I've been trying to work through the incompatibility issues with H.264 in native Vista apps. This might just fix most of it. From Red Herring:

This registry patch will tie MP4/M4V/M4A files into Windows Media Player [WMP11] and Windows Media Center [WMC]  allowing them to play this file type but also stream from WMP11 these file types to the Playstation 3 and Xbox 360  However there are caveats as it is not possible to tie a third party codec 100% into WMP without developing some sort of plug-in. Also available are patches for Flac, M2TS and MKV/MKA. I have moved M2TS off into it's own entry to keep it separate if you are looking for it click that M2TS link.

This process is compatible with 32/64-bit Windows XP/Vista with WMP11 present, Windows Home Server if WMP11 is installed should work as well. I would recommend though it is not necessary that you create a system restore point before applying these just so you have a point to return too.

Finally check out my H.264 video encoding guide for the Xbox 360/Playstation 3 as it will generate a compatible H.264 video & it covers pretty much all you need to know plus the limitations peculiar to each console though I primarily focus on cross compatibility in the guide. Also Windows media center extenders have the same H.264 profile as the Xbox 360.

Thanks Michiel