Hi. My 1st gen Air internal HD failed with bad sectors in the OS area. I removed it, set it up as a USB drive and reformatted it (presumably locking out the bad sectors) and reinstalled OS X Mountain Lion. I then reconnected the drive cable and reinstalled the drive. Unfortunately, the drive doesn't show up. When I start the computer while holding down the Option key, I get the screen that allows you to connect to a network, but the hard drive doesn't appear. I also created a USB boot disk using a 16gb thumb drive. When I start the computer while holding down the Option key, this drive does show up, but when I select it the Air doesn't boot. I was able to boot my iMac with both of these USB drives, so I know they are good. I'm stuck. I can find no reason for this. Does anyone have any suggestions? Thanks in advance.