Hi kinu,

which application are you using to play your files? Is that the default Media Player?

You could try to use the extra decoders pack: http://maemo.org/downloads/product/M...oders-support/

Or, if the pack doesn't work for you, give mplayer a try: http://maemo.org/downloads/product/Maemo5/mplayer/
It's a command-line app, you'll have to use the terminal, but it's worth.