ok, word of warning-advice. Be very careful with memory. Even though the package may say it is the same brand, same type, same model, that's not always going to mean they are the same memory. The silicon grades and internal timings can be different, which can mean that even identical looking sticks of RAM will not work with each other very well. This is the single biggest hazard with mixing 'sets' of RAM sticks. It is much better, more advisable, not to mix 'sets' and just get all your memory in one 'kit', so if you want 8G of memory, buy 2 sticks of 4G that come in the same package. This means they are the same batch, same timings, same silicon, same everything, and are therefore compatible.