What is your GarageBand version?
In my GarageBand '11 Version (6.0.5) the instrument library is installed in the system library:
/Library/Application Support/GarageBand/Instrument Library/
If there are instruments missing, you could try to restore them from your backup to this location. If this is not possible, you need to reinstall GarageBand. How did you buy it? Do you have installation media, or did GB come preinstalled?
The Loops Preferences added more sounds. Thanks!
And I will get Time Machine set up.
However, back to the library. I go to Instrument library, then to plug in settings, then to bass (for example), then to the first item which is Fingerstyle Electric Bass.pst Modified November 22, 2003 (4KB). I click on that and a licensing tab window pops up asking for name, organization, and serial number. I put in my name and serial number and a window pops up saying serial number is invalid. I and I checked it twice.
I know that some sounds are missing. For example when I go in Loops, Bass, the fifth sound down is Discopick bass. There are no number 3 or 4 sounds. It goes from number 2 to number 5.
I am going to check the second install disk tomorrow when I get a friend over who knows more about this than me. I don't want to make things worse!!
Many thanks, again in advance, for any help.