I have been able to get OGG playing in a limited fashion in ME by installing the OGGDS filter package.
http://tobias.everwicked.com/oggds.htm
These codecs are the only way
that I know of to allow playback of OGG files in WMP9. The first time you play an OGG file in WMP9 you get a Yes/No dialog box stating, "The file you are attempting to play has an extension that does not match the file format. Playing the file may result in unexpected behavior. Do you want to try to play the file?" Along with a, "Do not ask me this question again" checkbox. By checking the check box and clicking yes, Windows Media Player 9 will play OGG files.
When attempting to play OGG files in ME the same dialog box pops up. Clicking yes once makes the box disappear then reappear. Clicking yes on the second box will start playback of the file. The process must be repeated each time playback of an OGG file is started. Checking the "Do not ask me this question again" checkbox has no effect on this.
I am running win2k lite with DX9 and WMP9 installed and fully patched.
I am also using the latest versions of the mediaengine.exe and DB_UPDATE.exe
In addition I also have installed the OGGDS filter package.
http://tobias.everwicked.com/oggds.htm
I'm posting this as a seperate topic because it's not quite a bug, and not quite a feature request either. If the Dev crew cares to poke at making it work, that would be cool.
EDIT
I forgot to mention that I have added the OGG extension to the "Supported Audio Extensions" box in the Directories & Startup tab of the Settings menu.