Hello, Like others have done, I have just upgraded my internal HD in my iMac from 250Gb to 1Tb (Samsung Spinpoint F1 - HD103UJ). The HD was replaced without incident, hardware wise. It partitions, formats and reports correct size. But then the trouble starts.. The HD stalls a lot. Like, every once in a while all HD activity halts for anywhere from 5 to 30 seconds. Sometimes, the whole system locks up for a short time. The beachball appears a lot while it does this too. Then it loosens up again, until it stalls again a few minutes later. It does not happen that often, if there is very little HD use. All this is, of course, totally unacceptable. I have tried to restore my system from a SuperDuper! backup. Then I tried to restore from my Time Machine backup. Lastly, I tried a fresh install of Leopard. No matter how I install, it is always VERY slow (because it stalls a lot). I have also tried to force the drive to 1.5 Gigabit (SATA-150), but that did not change anything. I also tested the drive thoroughly with SAMSUNG's official ES-Tool, and the drive is all OK. I am out of ideas. Can the SATA controller (1.5 Gigabit Intel ICH7-M AHCI - supports AHCI v1.10) in the old iMac simply not handle a disk that large? Anybody have any thoughts on this? EDIT: SuperDuper! backup from old drive took 1h 40m. Restore from that backup to my new drive took over 4h..