I would stay away from deleting the default MOH files...
There are a couple of ways to turn off MOH. You can go into CCMAdmin and remove the MOH servers completely from your system (don't worry, you can always add them back in later). Callers on hold will then hear the Tone on Hold (described below) instead of music.
A less drastic approach would be to go to CCMAdmin --> Service --> Media Resouce --> Music On Hold Server, select a MOH server, and change the run flag to "No." This will unregister the MOH server (the Status will show "Not Registered"), and instead of hearing hold music, users will hear Tone on Hold (three short beeps every 5 or 6 seconds). Personally, hearing the Tone on Hold repeatedly makes me want to stab myself in the eye with a pen, but some people prefer it.
Other than the two methods listed above, I don't know of any other way to turn off MOH globally. Maybe someone else on this forum knows of other ways...?
TMH