PowerBook Medic is the ultimate resource for Mac computers and electronics repair. They have helpful tutorials on most Apple products including the MacBook, MacBook Pro, PowerBook, iBook, iPhone, iPod, and more, covering topics from disassemblies, to RAM upgrades, to replacement hard drives.
In this tutorial, learn how to repair hard drive and superdrive on an Intel iMac. Follow along with the video to repair the iMac. You can't go wrong with the instructions in this tutorial.