Hi, I just got a white Macbook 13.3 (2.1 GHz, Penryn) which originally came with just 1 GB of RAM (two sticks of 512 MB). Then I got two sticks of 2 GB Kingston RAM for this Macbook. I took out both 512 MB RAM and only put one stick of 2 GB RAM in, leaving the other slot empty. My Macbook works great. My question is, is it OK if I leave the other slot empty like that? Or should I put the other 2 GB stick in as well? Thanks a lot for your help.