When you open .OGG (Ogg Vorbis) file in Windows Media Player, the following error may appear:

This is caused by the lack of Codec that supports the .OGG file format. You can get the supporting Codec from Vorbis' site or from WMPlugins.

Download and install the above Ogg Directshow Codec, and Windows Media Player should be able to play the .OGG file. You may then associate the .OGG files with Windows Media Player.

Setting the file associations using the registry editor

1. Start Regedit.exe
   
2. Navigate to HKEY_CLASSES_ROOT
   
3. Create a new subkey named .ogg
   
4. Select HKEY_CLASSES_ROOT\.ogg

In the right-pane, perform the following:

1. Double-click (default) and set its data to mp3file
   
2. Create a new REG_SZ value named Content Type
   
3. Double-click Content Type and set audio/x-ogg as its data
   
4. Create a new REG_SZ value PerceivedType
   
5. Double-click PerceivedType and set its data to audio