Question : Problem: pc randomly beeps through the day

I have a user that says her pc sometimes beeps randomly throughout the day.  and it's very loud.  Some days it doesn't beep at all,  other days it does a series of beeps at 3 or 4 different times.  The series of beeps it does is seemingly random.  today it's 3 short beeps, but apparently sometimes it's just one beep or one long beep.  Sometimes it beeps even when she's not at her desk, but other people around her desk hear it.  Could I get some theory's as to what this could be?

Answer : Problem: pc randomly beeps through the day

you can also disable programs at startup, for testing if one is causing it :
run msconfig from the run box - in startup tab click disable all
reboot and test