I want to jailbreak and unlock my Iphone 3GS. It is on 4.2.1(8C148a) and the baseband is 5.15.04 Whenever I use Pwange tool it says it cannot find the IPSW. I have the IPSW file for 4.2.1 and restored with it. But Pwange tool doesn't recognize it and when I try to manual search for the ipsw it says it is the wrong ipsw. I don't know what to o or how to change it! I thought I was going about unlocking it the right way but I guess not. What do I need to do?