The only thing I have ever been told is to stay away from OEM stuff. Not only are the chips mismatched often, they are also usually chips that dont pass the tests and are sold to these "OEM" companies. OEM memory, unlike how it sounds, is NOT used OEM by computer companies. It is simply called OEM, and it is known for causing lockups, instability, and other issues. Stick with Micron, Kingston, Crutial, or any other name brand that offers lifetime warrranty. I am currently using a lesser known company called Kreton, and I am having great luck with it as well. It was $68 for a 512mb stick of pc3200 which works flawlessly in my M.