Thanks in advance for the help and sorry if I'm posting this in the wrong area I'm new to this forum I've been trying to play some games on my mac but they were lagging so I figured I would try adding ram. So I went to best buy, told the guy I have a mac book pro and he gave me this to buy and said to youtube it to learn how to install: PNY 8GP 2x4GB Dual Channel PC memory kit (mac's too), compatible with 1066MHz. The mac that I have is: Mac OS X, 2.4 GHz Intel core 2 duo. Memory: 4 GB 1067 MHz DDR3 When I put the new ram, I turned on my mac and it wouldn't even open, it was stuck on the white screen with the grey apple and it paused when trying to load.. wouldn't even bring me to the screen. I put the old ram back in and it worked fine. Then I put in 1 of the 4 GB of the PNY ram and it didn't work either. Do I have the wrong ram, did I do something wrong installing? I'm fairly sure that I installed it correctly.