I installed a Samsung 120 GB harddrive from iFixit. Removal and installation was easy with iFixit. The previous drive was bad. I erased the new harddrive with Disk Utility and selected the recommended MAC OS Extended (Journaled). The new drive shows with the named partitioned file. I installed the original Macbook Air installation disk 10.5 in the Macbook Air external Super Drive. When I attempt to install I get the above message. I Erased again, got the same disk info,/Volumes/xxxx's Airbook, format Mac OS Extended (Journaled), 3 folders, 3 files 111.4GB available, Verify disk is OK.

I also have a new 10.6 installation disk but I can't get the 10.5 disk out of the external drive.

Why am I getting the "cannot install on this computer" message and how do I correctly install the 10.5 software?

How do I eject a startup disk from the external drive when the install disk is not available to Eject or the Drive itself cannot be ejected because the disk could not be unmounted?

Thank you