• Connect the phone to PC and Power off the phone
  • When the phone is powered off, power on the phone and hold the power key (Green) for three seconds
  • Keep pressing the power key (Green) and at the same time press the home button (Blue) for 10 seconds
  • Release the power key (Green) and still pressing the home button (Blue) until the PC detects the phone in DFU
  • On DFU Mode iPhone must have blank screen 
How to enter Apple iPhone 2G into DFU Mode
Apple iPhone 2G DFU Mode