iPhone 3Gs users have nothing but headaches when it comes to jailbreaking their iPhone. A lot of confusion about ECID, IBSS and IBEC files… FSMdotCOM tried to explain how it works, and why you need to save your iPhone’s certificate.
difrnt.com made available to us a free utility that helps us to downgrade our iPhone 3Gs and offers us step by step instruction till the point we get the device into the DFU mode. From there you can use this tutorial to continue.
3Gs Downgrade Assistant is free and for Windows ONLY. You can download it from here.