I am preparing an iMac to be sold/given away, and I am planning to erase the hard drive and re-install OS 10.6 (it is an older iMac). I have the Mac OS X installation on USB and I am at the step where I access Disk Utility after booting from the USB. Here is my silly question: Which Disk do I select to erase? The one called "Macintosh HD" or the one with the manufacturers name? If I select "Macintosh HD" should I also Erase Free Space first? I notice that if I select the Manufacturer-named disk, the Erase Free Space is not available (I assume because it will erase the entire drive). Any help is appreciate!