google "gspot codec" and download/run the program GSpot. drag and drop the UPK file onto the window and it will tell you what kind of file it is (mp3, wav, etc.) if it's readable. I'm not aware of any converters, but google is the first place to go and search.
If it is readable, and it says like WAV or MP3 - then change the filename extension to .wav or .mp3 accordingly and play in Media Player.
[Edited by opfor, 1/14/2009 2:13:49 PM]
i tried that out, but it doesnt work for these upk files.