Hmm, it could be the onboard sound on the laptop that could be the prolem here I'm afraid since it happens like clockwork every 5 mintues. I know for sure theres no button or setting that would make the sound do this.
Have you tried connecting headphones to it? I would guess you'd get the same thing though.
It could be the sound drivers though. Is there anyway you can figure out this? Go to Start, Control Panel, and go to Sounds and Audio Devices.
Go to the Hardware tab of this. What name of the sound card does it give in the top one there listed after the cd drive drivers?
If you can, search for these drivers on the internet, and download some new ones from the right site, most likley the manufacturers site after searching for the model, and then try re-installing the sound drivers after un-installing them using the Hardware tab of that window you had up. Just select that driver with your soundcard on it, and go to Uninstall driver, after opening up properties.
Then restart, it should then see the sound card when windows boots up as having no drivers yet, you'd then simply ask it to browse and select the drivers you have just downloaded to a location, unless its an EXE, in which case it would do it automatically after uninstalling the drivers
Or you could post back with the name and we could search for it if your unsure
If this didn't help, we'd know its the onboard sound itself, but in a way, it seems too like clockwork and would suggest a driver issue.
Hope I can help