I probably do that. But I find it strange I cannot turn that stupid sounds off. I've got two pc's, both with an legal version of XP Home: both the same problem.
What if you deleted or renamed C:\Windows\Media\Windows Navigation Start.wav? If it still needs that file there you could create a wav that was just blank (no sound) and name it 'Windows Navigation Start.wav".
Those suggestions really sidestep the issue though. Something is going on/isn't right with your system if you tell it not to play a sound for that and it does...