This works with iPhone 4(AT&T), iPhone 3GS, iPod Touch 4, iPod Touch 3G, and iPad 1
This DOESN’T work with iPhone 4(verizon) and iPad 2
iPhone 4 Unlockers don’t do this, Ultrasn0w isn’t ready.
On Windows make sure to right click on Redsnow.exe and run it in Windows XP SP3 Compatibility Mode and as Administrator.
Update your device to iOS 4.3.1 before you do this guide.
Update iTunes to the latest version before you do this guide.
Head to the link below to view the step by step procedure.
From TY iPhone Help via Daily Iphone blog