Video files not being recognised in Media Centre?
If Vista's Media Centre isn't picking up your random video files such as MKV, TS, MP4, etc but you've already got the codecs installed, a small registry patch can fix this by changing the PerceivedType to video.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.file-extension]
"PerceivedType"="video"
(Emphasis is what you need to change for your desired extension)
Copy the above text (modified of course), into a text file, save as .REG, double click on the REG file, and restart VMC. All done!
For me, I needed MP4 and TS, so [HKEY_CLASSES_ROOT\.ts] and [HKEY_CLASSES_ROOT\.mp4]