While downgrading iOS 4 to iOS 3.1.3 firmware or trying to restore to custom firmware you might stuck with error 1015 in iTunes. To fix or troubleshoot error 1015 application Error 1015 Fixer is just what you need. Here is how to solve the problem in one click!
Step 1 - Download the utility Error 1015 Fixer for Windows
Step 2 - Install LibUSB (download Link)

Step 3 – Once you get the error 1015 just start Error 1015 Fix and click on Fix My error!

Step 4 – Now click on Done! Click to exit!

Voila! Error 1015 has gone!
