Though you can't easily replace an iMac's G3 processor, there are at least two other ways to improve your iMac: increasing the amount of RAM, and replacing the hard drive with a roomier one. If you have a Rev. A iMac, you can also supplement your computer's video RAM. We'll show you how to accomplish all three tasks. The first set of steps (1 through 6) applies to the tray-loading Bondi blue and fruit-flavored iMacs; the second set is for slot-loading fruit-flavored models and for every iMac since.