STEP 1. First you have to launch iTunes 10.1.2 and then follow the steps posted below to put your iOS device into DFU mode.
For iPhone, iPod touch and iPad:
- First connect your iPhone, iPod touch and iPad with your computer.
- Now you have to hold simultanesously both Power and Home buttons for ten seconds.
- Release the Power button but keep holding the Home button for ten more seconds.
- Now your iPhone, iPod touch and iPad should be in DFU mode.
For Apple TV 2G:
- First you have to connect your Apple TV with your Computer via microUSB
- Now simply restart Apple TV by holding down Menu + Down buttons together for six seconds.
- Now immediately you have to hold Menu + Play button until iTunes shows you the message that Apple TV in recovery mode is detected.
STEP 4. Now again you have to start iTunes and then from the sidebar simply choose your iOS device. Now you have to press and hold left “alt” button and then click on “Restore” button in the iTunes and then simply release the “Shift” button. Now choose the required custom .ipsw file and restore it.
Now iTunes will restore your iOS device to the latest iOS 4.2.1 custom firmware without any error. You can download iREB RC3 for Windows from here. In this way you can fix 1604, 1601, 1600, 16xx restore error in iTunes with iREB RC3.