Couldn't find anything about cn memory in the search function. I have a Macbook pro 13' 5.5 2.26gh that came with 2gb Ram. I was advised to install 2x 4gb RAM, but when I powered up my macbook it made a beeping sound and wouldn't start up, so I re-installed my initial 2x1gb memory and it worked fine again. This has lead me to believe that perhaps my machine can only take 2x 2gb, but it will be my 3rd return to a store that has lead me astray twice now, so am just wondering if Cn Meomory is not compatible with my computer, or if I'm just putting too much in. Have lost all faith in the "experts" at the store so am hoping someone here can shed some light? Could it be an incompatible brand of memory? Thanks in advance!