im trying to upgrade the memory in an old 13" macbook model MB061LL/B with PNY 2gb ddr2 pc2 5300. The problem im running into is that when i put the new memory in either nothing happens or i get 3 beeps. ive been able to get 1 stick of the PNY memory and one stick of the factory memory to work. Using this ive determined that both sticks of PNY memory are working properly does any one have any suggestions on why i cant get both sticks of PNY to work at the same time??