Custom Soundtracks question

I got the Xbox 360 a couple weeks ago, and just started getting the hang of custom soundtracks for certain games. The C.S. works for my wrestling games(i.e. WWE SVR 2010, WWE L.O.W. etc...), But I was wondering can youplay C.S. for regular Xbox games on the 360? I tried the C.S. on Tony Hawk's American Wasteland(Regular Xbox) and GTA San Andreas but they didn't work. I thought I was doing it wrong, because for the WWE SVR games each song had to be it's own playlist.

does anyone know?

All you need to do is start the music player in the dashboard before you start the original XBOX game