When you use a computer and software enough, sooner or later there'll be a problem (though these days it's mostly later — much later). But let's say you boot up Garage Band and suddenly all your loops or your software instruments are gone. What do you do? First off, don't panic. Verify all your disk permissions and repair them if need be. Then verify that your hard drive doesn't have any problems. You can do both processes using the Apple Disk Utility, which is in your Applications folder, inside the Utilities folder. If your hard drive has problems, you'll have to reboot using your original OS X installer DVD, then use Disk Utility to fix whatever problems you might find. If neither fixes the problem, check to be sure that your loops and instruments are still where they should be: User (home) > Library > Audio. If you don't see Apple Loops, Plug-ins, Sounds, Presets, or MIDI Configurations there, use Spotlight to locate these (odds are good they'll all be in the same place). Drag them back into the Audio folder and then restart Garage Band. If that still doesn't solve the problem, try reinstalling Garage Band from your iLife '06 installer disc.