I was going to get a total of 3GB of RAM on my brand new 24 inch iMac 2.4gz intel core 2 duo. However, I brought a 2x2GB from OWC (macsales.com). I was going to give one 2GB stick to my brother to put into his new Santa Rosa Macbook so he would have a total of 2.5 GB of RAM in his Macbook and I would have 3GB. After going to the apple store, it was not recommended for my brother to have mismatched memory modules in his Santa Rosa Macbook. So now I am stuck with 4GB of RAM plus the one GB of RAM that came with the iMac. I installed the 2GBx2GB of RAM and also tested it with 2GB +1GB of RAM. Honestly I could not tell the difference. The machine, while it launch programs much faster than the originally 1GB RAM that came preinstalled going from 3GB to 4GB did not make too much of a difference. Do you think it would a difference to have 4GB if I were to run Windows Vista with Parallels vs 3GB. Will Vista be faster with 4GB if I were to install it via Boot Camp? What if I installed just Windows XP with either Boot Camp or Parallels. I do minimal video editing. Memory is so cheap these days anyways so I doubt I am going to return the 4GB of RAM. I might craigslist my spare 1GB for cheap and at least recover my overnight shipping costs!