Ahh ... Had you said your old OS 9 System Folder, and that you did a clean install, I should not have thought OS X. But why 'A & I', then? You can reactivate the Previous System Folder, by carefully renaming:

1) the current System Folder anything but that name, eg Oops, and

2) the Previous System Folder as System Folder, and

3) the renamed Oops folder as Previous System Folder,

as long as you removed nothing (extensions, preferences, control panels) from the Previous System Folder while it was resting. If it was scrambled in some way, of course it will still be scrambled. However, why reuse it if it was thought to be worth replacing?

de