I purchased the 4GB Kit (DDR3) from Fry's yesterday and installed it today. The model is CT2CP25664BC1067 and supposedly works with the Aluminum Macbooks. Everything worked fine and OSX displayed 4GB and Windows XP shows 2.72 GB of Ram. The problem was when I tried playing a few games tonight, Fallout 3, Lost Planet and Mirror's Edge. All three of them were noticeably choppy and had horrendous frame rate issues compared to the stock 2 GB of ram. Maybe I purchased the wrong Ram, but I was really surprised that the increase negatively impacted my system performance. Is the Aluminum Macbook more particular about the brand of Ram that works with it? I guess what I am looking for is which ram provides the most solid and stable performance with the Macbook and would help me see a boost in frame rates versus what I am seeing with the Crucial 4GB of ram.