4 error beeps on a

this sounds like the ram problem open the pc or mac case make sure you remove power cable from powersuply and once inside look for your ram sticks and have a peice of toilet tisue and some cotton buds to hand carefully remove your ram sticks and place them onto the toilet tissue and one by one you will clean the contacts along the ram stick holding them by the sides using the cotton buds when you have cleaned both sides of them place them back onto the toilet tissue then place one back into the pc or mac motherboard and replace powerlead back into power unit then power up pc or mac then if this gives you beeps place this to one side repeat for all ram sticks to find out if you have any that need replaceing.
and close up case with ram stick that are ok.

Best of luck with this one