Hey, I've got the latest iMac and I just upgraded it to 4GB of RAM and now I've got these two 1GB sticks left over. My parents have the previous version of the iMac (still Al) which uses 667MHz RAM and I'm wondering if I can install my old RAM in their computer. Obviously it wouldn't be able to take advantage of the higher speeds, but they currently only have 1GB so upgrading to two would be useful. The basic question here: is RAM backwards compatible? Thanks.