MC only disables the sounds on startup, so if you enable sounds once MC is running, you'll hear them until you restart MC.
I do not ever add/subtract/enable/disable system sounds after the install of XP, Office 2003, and MS Office sounds. I had to find the settings and look for the right noise to troubleshoot this.
MS Office sounds have nothing to do with standard system sounds like the Windows Explorer->Start Navigation sound.
To test if that was the source, I had disabled that sound. I then get no noise when tracks change. I also uninstalled Office sounds just to remove that as a possibility.
Today I opened the sound control panel and set it to the Windows Default sound scheme. That enables the Windows Explorer->Start Navigation sound, and I am going to guess that is the way it is set at XP install.
Once the system sounds are back to default, I always get the noise as I described when I started this thread.
It does not matter if I stop MC, start MC, reboot. When MC is running and I am in PlayingNow I get the sound. If I am elsewhere in the tree and go to Playing Now I get the sound.
If it is supposed to be disabled when MC starts, it is not on my machine or on the others who posted in this thread.
If the answer is to disable the sound manually, that's fine too.