I tried upgrading my daughter's 2.16 Ghz Blackbook from 2 GB to 6 GB tonight. It won't boot up. It sits there flashing the standby light. So I pulled 4 GB out of a Whitebook and put that in. It boots fine with 4GB but not 6. Oh well. It's probably twice as fast for her now. Looking at the bright side, at least now I know what a Macbook does when it doesn't find memory it knows what to do with, and at least she has a somewhat faster machine now. Another good thing is I found out her battery is bulging. I'll take it by the Apple store and see if they have a replacement.