I'll probably be upgrading the small 20GB HD on my 500 MHz slot loading indigo iMac in the next week through newegg. I've found some pretty nice ones that are ATA100 with 8 MB cache and obviously limited to 120 GB. Now the question is whether or not the ATA100 is fine with installing an internal HD into the same slot with the same connectors or will they change. Does it have a max of 33 anyway and therefore I should worry about the other parameters besides the 100? I was under the impression that the maximum in this computer is an ATA33.