Hi, I replaced the hard drive in my iMac 24" 2.16ghz core 2 duo when it died. I have tried reinstalling from the original 10.4.7 disks but the wheel under the apple logo freezers after around 1 minute. I have cleared nvram and the hardware check says everything is normal. I bought a new retail copy 10.6.3 and this stops during install asking me to turn power off to reboot. I have tried installing holding the left shift key and then I get the following message: unable to find driver for this platform "ACPI" Any help appreciated please. Thanks.