I have an imac with Mac OS X 10.5 on it. Here is what happened: I wanted to network my imac with another pc in the room that has Windows on it. I set permissions to allow read write access for other computers on the network. The pc on the network were displayed on the imac but could not be opened when clicked on. Message box stated needed to reboot imac. On rebooting the imac all that comes up is grey screen with apple symbol and gear running underneath it. Tried booting in safe mode-screen displays progress bar.Progress bar completes and then goes away and then all i have is a grey screen with an apple symbol and rotating gear. Also tried resetting the PRAM which ended with same result of grey screen,apple symbol and running gear. Have recently moved and can not find my install disc. Help.