A. You need to re-install GB from its install DVD, it should be on one of the discs that came with the computer, likely labeled: Software Restore, or Additional Software, or some such, if not an iLife disc itself. It may also simply be an installer on one of the restore discs called "Bundled Software", "Additional Software" or something similar. If you wish to only install Garageband and/or its ancillary files, use the Customize button when it appears to allow selective installation of the software you want.
GarageBand from Apple Computer uses audio loops and MIDI loops in Apple Loops format. It can work with Audio Units plug-ins. Apple Macintosh Compatible FireWire and USB interfaces can be used to connect Audio and MIDI instruments to your Mac, and be recorded into GarageBand.
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