Q: I upgraded to iOS 4 and now my iPhone 3G is slower than ever. How can I go back to the old settings?
A: If you're still using an iPhone 3G and tried upgrading your phone's software to iOS4, you've probably found that it's become little more than an expensive paperweight. The newest operating system works fine on the 3GS and the iPhone 4, but it's too demanding for the 3G to handle properly. The phone slows down to a snail's pace. Here's how to downgrade your iPhone iOS 4 to iOS 3.1.3.
Before you attempt to downgrade the operating system of your phone, make sure that you back up all of your contacts and personal information on iTunes and your computer. In the processing of downgrading, everything will be wiped from your phone.
Once you've backed everything up, find a copy of iPhone OS 3.1.3 (iPhone1,2_3.1.3_7E18_Restore.ipsw). You can find this online or a on your computer. If you're using a Mac, it'll most likely be located in the iPhone Software Updated folder (Macintosh HD > Users > Yourname > Library > iTunes > iPhone Software Updates). If you're using a PC, this file will be in the iPhone Software Updated folder at C:\Documents and Settings\Yourname\Application Data\Apple Computer\iTunes.