I had bought 4 GB memory stick a couple of years ago and the brand of ram was AXL which was unknown to me. However mine booted up fine with it installed and all was well so I thought. However, the underside of Macbook Pro was running hotter than it used to be and a shorter battery life. After a year or so, I took it out and replaced it with another 2 GB ram, it runs cooler and the battery life is better. Could it be to do with a cheaper unknown brand of ram? Does anyone have any issues with their 6 GB 2007 Macbook Pro? And what make/model of their 4 GB ram?