Found it today!
I've found this at Apple Discussions web:
We must thanks GangstaPenguin!!!
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Posted by: GangstaPenguin
Registered: Sep 12, 2009
Re: Downgrading iTunes 9 to 8
Posted: Sep 12, 2009 2:45 PM
Actually, downgrading is an option.
1) Quit iTunes.
2) Delete iTunes from your Applications folder.
3) Go to your ~/Music/iTunes folder. Delete or rename the "iTunes Library" file.
4) Open the "Previous iTunes Libraries" folder and look for the backup of your old pre-9 library; it should be dated at about the time you first ran iTunes 9. Copy it back out to the ~/Music/iTunes folder, and rename it to "iTunes Library".
6) Go to
http://support.apple.com/downloads/iTunes_8_2_1 and download iTunes 8.2.1. The page says it's for G3, but the Read Me file says it'll run on G4, G5, and Intel too. Open the diskimage and run the installer.
You should now be able to run iTunes 8.2.1 again.
And your iTunes will restore to before you upgraded and you won't lose anything.
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