Ideally you would avoid converting between compressed formats ( MP3 to OGG ) because you lose quality each time instead of just once. I'm guessing that Music2000 doesn't export to an uncompressed format? ( EG: Wav ) I suppose if you export to a very high MP3 quality, it might not be too bad.
RE: Mpeg Movie codecs. Don't use MP2, a lot of people don't have an MP2 decoder any more. MPEG1 is very safe, and I don't think there are any legal issues with it, but you'd want to verify that with someone. MPEG4 is another option ( XVID uses MPEG4 ) but I really don't know how widespread MPEG4 codecs are.
RE: Mpeg Movie codecs. Don't use MP2, a lot of people don't have an MP2 decoder any more. MPEG1 is very safe, and I don't think there are any legal issues with it, but you'd want to verify that with someone. MPEG4 is another option ( XVID uses MPEG4 ) but I really don't know how widespread MPEG4 codecs are.