http://www.tesnexus.com/downloads/file.php?id=8516 was an effort long ago to create a source port for Arena. It never got done, but this tech demo can extract the sounds, music, sprites, and textures from the original game. It only works with the floppy version though, so if you have the CD version, download the free copy of Arena off Bethesda's site and use WinArena on that.