I have recently purchased a 12 inch Powerbook (comes with 512MB RAM as 2x256). My sister has just purchased a 12 inch iBook (with 256MB RAM). She won't be using it for anything intensive, just the usual web browsing, email, itunes and office apps, so initially 256MB might be enough but I think she should probably upgrade it to 512. If I decide to upgrade the RAM on my machine, then can I give her the spare 256mb stick from my Powerbook? The PB RAM is DDR PC2700 (whatever that means) whereas the iBook takes PC2100. I'm sure I heard somewhere that you 'can' use it, but would this give worse performance than buying the PC2100 because it doesn't match the built-in module? Any advice greatly appreciated, thanks!