Just received a new Mac Mini and I went to switch out the hard drive to a 7200rpm drive. I dont have a thunderbolt cable for target disk mode so I was going to install Mountain Lion off the bootable disc I made for my iMac. I was using an external optical drive and when I boot the machine holding down the Alt key - I can see the disc but when I select the install disc I get the circle with a slash through it on my screen instead of the Apple logo. Ive used this disc several times before. Is this not possible from an external optical drive or is there something Im missing? I guess I can always download 10.8 from the App Store again and make a USB installer if I need to - was just trying to avoid that since it takes so long to download.