Hi, I just purchased a macbook with 2G's of memory. I am thinking of going 4 gigs. I know the configuration I have is 2x1G dimms. How many dimm slots are supported for the macbook? For me to go 4G's, can I purchase another 2G's and call it a day, or do I have to buy 2 2G dimms? Also, what is the most affordable way doing this? Thanks in advance!!!