Apple ipod

How I can update my iPhone from 3.1.2 to 4.0?

always gives me an error and I suspect it is because I do not 3.1.3, but does not give me the opportunity 3.1.3 obtain 4.0 DFU mode is and how I can put on it

I updated and the phone will go down, I do not know if your software or a fault on my phone

Spirit Jailbreak for Iphone 3g 3gs 3.1.2, 3.1.3, 3.2 and Fix Error c0000005 on Windows 7