How to Pre-install new iOS 4 to your iPhone or iPod Touch
In this clip, learn how to install OS 4 on your iPhone or iPod Touch before it is released to the public. This is not the final Apple approved version, so you will be missing some small things like wallpapers and iBooks but you should still have plenty to play around with while you wait for its official release!
1. Download the iTunes 9.2 Beta
2. Install the iTunes 9.2 Beta
3. BACKUP using iTunes 9.2
4. If you are Jailbroken use APTBACKUP to Backup a File List of your Jailbroken Apps.
5. Download the correct .ipsw for your Device
6. Go to iTunes and on your iPod's Page, HOLD OPTION-ALT and click RESTORE and choose your .ipsw
7. After that wait and then you have a fresh Install of the iOS 4.
8. You can now restore from your backup.