desktop or laptop, computer make/model or motherboard manufacturer and CPU
some bios' s will sound an alarm when the CPU reaches a certain temperature and then will shut down if it gets too hot. you have not experienced a shut down have you ?
this of course is just a shot in the dark but beeps provide error information. what you describe sounds like an alarm. i would remove the side panel (if desktop) to confirm that the CPU fan is spinning.
also, fan could be spinning but dirt, dust, lint could be defeating the cooling process. if this is the case you should read up on cleaning your computer before grabbing the vacuum cleaner.
Edited by caperdog, 11 May 2010 - 08:07 PM.