If you boot into the CMOS/BIOS setup, there may be an option to disable the beeps. The reason for the beeps is that in the event of an error, the computer will produce a unique beep sequence per error type. You can the. Look up the beep code and figure out what the problem is. This is very helpful when there is no display.
Most desktop PCs will beep to confirm that the POST (Power On Self Test) has completed successfully. This is not the case with most modern laptops, however most laptops and desktops will beep when an error condition prevents them from completing their power on self test.