maybe nothing to do with this, but have you got sticky keys turned on in windows xp ? if so turn them off as if you hit shift or alt or control 5 times within a set period of like 5 seconds or so, your pc will beep and sticky keys will be turned on and they basically act as shortcuts for whatever and can be a pain in teh butt, also for your pc to beep, holding down 3 keys on your keyboard at the same time will make the pc beep, not all of them mind you, just some will make the beeping noise if you have held or pushed 3 keys by mistake.
i know i am again late to the thread, but it may help, probably not.