DirectShow filter installer does not add proper "PerceivedType" REG_SZ to HKCR\.ext key
I just ran the installer (http://downloads.xiph.org/releases/oggdsf/oggcodecs_0.81.15562-win32.exe) and found that while Windows Media Player 11 recognised my .ogg files as playable, it unfortunately wouldn't show them in the Library.
Found a link to a Microsoft page on enabling this functionality: (http://msdn.microsoft.com/en-us/library/dd563763%28VS.85%29.aspx)
In short, aadding a string value named PerceivedType of either "audio" or "video" to the HKEY_CLASSES_ROOT.extension key enables this to work.
Please add this to your installer.