Dev Team released the new Pwnage tool 3.1.3 to Jialbreak iphone 3GS 3.1 on MAC. But this one is not apply for the windows users. But don,t worry here is the Guide which will help you to Unlock iPhone 3GS Firmware 3.1 on Windows. Yes i tried it this on my iPhone 3GS on Windows
Unlock iPhone 3GS Firmware 3.1 on Windows | TechnoBuzz.net
Unlock iPhone 3GS Firmware 3.1 on Windows | TechnoBuzz.net