How do I get my I9000 to play a specific folder of musics

When I use Galaxy s I9000 built in music player to play my music, it doesn't just play musics from default media folder, it also throw sound tracks from installed game folders into the mix. I guess the phone just scans whatever sound tracks it can find from internal SD everytime it starts up...

So how can I get it to just play musics from my default media folder?

If the solution is to use other apps, which one is recommanded and support I9000's 5.1 sound system?

thanks in advance