Currently Being ModeratedDec 17, 2012 5:21 AM (in response to Chomp1994)
That is where your Instruments Library should be: In the top-most folder "Library" on your system drive:
/Library/Application Support/GarageBand/Instrument Library/
If you cannot replace it from your backup, you need to reinstall GarageBand.
I also tried reinstalling applications install DVD that came with the iMac.
In what way did the reinstall not work? What is the problem?
What is your MacOS X version? Is your profile signature 10.6.8 still correct?
If you have a newer system, see here: