Hi! I would like to ask questions to Mac experts!

I have installed Windows Media Player 9 for MacOS X and also Reaplayer 10 (the free version) in order to player their files (.asf and .rm, etc).
BUT! I have to sound on both of them! On Windows Media Player, it says that the codecs are not appropriate / found, and on RealPlayer, it doesn't say anything, just no sound.
I also want to say that on VLC (for other movies, not real or media player), no problem, there is sound, as there is also sound for System sounds...
I have a Powerbook G4 17" and I don't understand why those 2 applications don't work.
Thanks a lot for your help!!!