Can't play mp3,wav,...

Hello!
I have three OS 's on my PC:windows XP,
windows 98 and Linux RedHat 8.0.
I have installed it about a month ago.
My problem is that when I mount my windows drives and
go through my folders there when I want to play my
music files there i.e mp3
or wav it opens XMMS and it opens a dialog box for
selecting the file but it does nothing when I choose a
file.
I have a GIGA mother board and its sound card is
onboard.It is necessary to say that I have played some
musics by my RedHat Linux.
I think it was .wav file,but actually it was by
chance.
I would be happy if anyone answers my question.
Bye!


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