I have a bottom of the line 512 MB Memory macbook, and I am considering updating to atleast 1GB. I was looking at my activity monitor and it says about 506 MB is being used as I am doing fairly simple tasks such as using iTunes, web browsing, and using Adium. However it says that about 100 MB of that is inactive. What exactly does this mean? This doesn't mean that it is available for use does it, because then I would not be using 506 out of 512 MB of my memory correct? Anyway I was just curious what it meant for memory to be inactive and if I should upgrade to atleast 1GB. Any advice greatly appreciated.