computer makes beeping noise upon boot up

One beep on completion of power on self test is normal.

 

If it's a long series of a lot of beeps, you probably have a key stuck.  If this is the case, make sure none of the keys are pressed.  If you spilled anything on it recently it may be causing the keys to stick, so try to clean inbetween the keys with a q-tip or just let the problem fix itself.