We know that iphone dev team released Pwnage tool 3.1.3 to Jailbreak both iPhone 3GS 3.1 Firmware and iPod Touch 2G 3.1 Firmware.
Pwnage tool is only for Mac Users, and there is no information from iphone Dev team when Redsn0w will available for windows users.
However, we are sharing a tutorial on how to use custom IPSW to to jailbreak iPhone 3GS 3.1 firmware on Windows systems. Thanks to saad for sharing custom firmware.
Steps to Jailbreak iPhone 3GS:
1.First downland custom iPhone 3.1 Firmware from below links
2.Now join above downloaded files in to a single file with the help of HJSplit and extract that file.
3.Install or run iTunes 9,now connect your iphone to the PC
4.Select your iPhone from devices menu,then while holding SHIFT key click “ Restore” and select downloaded custom IPSW file
5.Wait until the installation process complete,after jail breaking follow below steps to unlock your iphone & use it with any Carrier.
6.Now Run Cydia to install Ultrasnow
7.Add repository,by typing repository URLhttp://repo666.ultrasn0w.com/
8.Now Search for Ultrasnow, install it.
9.After installation, restart your iPhone 3G and insert your SIM.
10.That’s it! Now you can use your iphone with any carrier
custom firmware links Credits sizlopedia