Hey guys, I'm pretty experienced with Macs and RAM and everything and I've tried of everything I could think of which didn't help at all. I currently have an early 2008 MacBook (MacBook 4,1) that I bought about a month ago from a friend. It still had the stock 1GB of RAM (2x512MB) when I got it so I went over to newegg and ordered a GSkill 4GB (2x2GB) kit. Prior to pulling the trigger I read all of the negative reviews, found nothing mentioning compatibility problems with macs. Then I skimmed through the positives finding many success stories of this RAM with macs. When the RAM comes I put it into my MacBook and it won't boot. I then put one 2GB stick in with one 512MB stick. The machine boots this way and recognizes the 2.5GB of RAM but it won't boot with the full 4GB. According to MacTracker this machine will take 4GB according to Apple and will actually take up to 6GB in the real world. I tried resetting the PRAM as well as the SMC, neither made any kind of difference so I'm stumped. I'm under the impression that if the machine will boot with one of these sticks in it should boot with both. The only odd thing I did notice is that the machine will not boot with just a single 2GB stick in there and no 512MB stick. It shows the same symptoms as having the full 4GB in. Any advice as to why this RAM isn't working so I can return it and buy some RAM that will?