im05

1. download 4.0.1 IPSW to the computer

http://appldnld.apple.com/iPhone4/061-8616.20100715.phnt4/iPhone1,2_4.0.1_8A306_Restore.ipsw

2. connect iphone (open itunes if it doenot starts automatically)

3. press shift + click restore button (option +click in Mac). Browse the ipsw downloded in step 1.

4. after restoring. jailbreak (visiting jailbreakme.com) and unlock with ultrasn0w