Apparently several iPhone packing users have been experiencing several errors in iTunes during firmware restore and have been asking via numerous sources how to fix errors 1604, 1603, 1602, 1601 and 1600 reports an article over on redmondpie

Apparently said error happens when the user tries to restore their jailbroken custom iPhone 3.1.3 .ipsw file. So they have come up with a fix for this problem using iREB for Windows, which is iTunes Restore Error Bypasser and can bypass said error when restoring .ipsw file in iTunes.

The latest version of iREB does work with iPhone 3.1.3 firmware running on the iPhone, iPhone 3G and iPod Touch 1G and 2G and heres how it works…

Start iTunes and place the iPhone in DFU mode, press and hold Home and Power buttons simultaneously and after 10 seconds release the Power button while still holding the Home button until iTunes shows a message saying it has detected an iPhone recovery mode and your handset screen will remain black.

Close iTunes and start iREB on Windows, select your handset and wait for a red or white screen on your handset. Open iTunes, selects your handset from the iTunes sidebar, press and hols left “alt” or “shift on Windows” on the keyboard and click “Restore” in iTunes then release”Shift” and select a custom .ipsw file and restore it, job done.