PuT YOUR iPhone INTO DFU MODE.

Method one.

• Turn off your device.
• Hold down power and home button.
• When you see the Apple logo, release the power button but continue holding the home button down.
• Open iTunes and wait for it to tell you that its in restore mode.

Method two.

• Download this
• Extract the archive to the root of your hard drive, should be C:/DFU/
• Connect your iPhone and ignore iTunes
• Goto Start – run
• Next type in “c:/dfu/dfu iBSS.m68ap.RELEASE.dfu”
• Wait for iPhone to show a “white” screen
• Now you may proceed to downgrade!

**also these files are found in ibrickr’s directory except for the .dfu file**

Source