I have tried everything I can find to help me on this site so I am forced to post anew. Forgive me if I have missed a thread. I have a 3 year old iMac which froze completely on me. Start up gets as far as the grey screen and spinning gear, with loud whirring sound from the fan. Fortunately I have backed up on Time Machine so I have no issue with erasing data. I am attempting to reinstall from the Leopard software (which had been installed for some time and worked fine). The software discs are also fine. No strategy is working to get past that grey screen. I have tried restarting (with Leopard disc in place) whilst holding down the c-key, the alt-key, the command+alt+ p+r keys. No progress past that grey screen. Is there another option to try before I assume I have a hardware issue? All wisdom gratefully received.