Have you been using the iOS 5 beta and want to go back down to iOS 4.3.3? You will also need to downgrade iTunes 10.5 back to iTunes 10.3.
Here’s how to do that.
1) You will first need to uninstall iTunes. Just go into your Applications folder and toss it in the trash bin.
2) Now go to Apple’s iTunes site and install iTunes. It will be version 10.3.1. You can do it here.
3) You may get an error. Don’t worry.
4) Go to ~/Music/iTunes
iTunes 10.5 upgrades the iTunes library file and won’t let you downgrade, so you will need the prior version library file. Here’s how to go about that
5) You will need to rename iTunes Library.itl to iTunes Library.bak
6) Go into the “Previous iTunes Libraries” folder where you will find several files with dates in their names. The most recent one will have the .itl extension, but the others don’t. Copy that to the parent folder ~/Music/iTunes/ and rename it iTunes Library.itl
7) Congrats. You’re done.