to activate a sound (WAV File) for a operation on the PC. E.g when you recieve a email you usually get tune or when shutting down windows you can also get a Loggoff tune.
Different PC's some by defualt or some set by how you personally want them to react with there very own tune or noise.
Sop say you want a certain tune or noise to play when you open a programme you can tell windows to play this when you carry out the task.
All this is done in the Control Panel in the "Sounds" Icon or possibly Multimedia & sounds, depandant which Windows you have.
In there you will see the commands and below you will see the type of Audio WAV file/Tune or noise you can set to that command.
So it sounds like a Wav file tune or sound has been set to react to your Mouse. It could also be set via any 3rd party Mouse software if it supports these.
It doesn't seem to be a problem you have, may be you have just got XP and are new to it.