A few days ago, the iPhone dev team released the PwnageTool 2.0.1 to jailbreak the iPhone 3G. That tool is only available for Mac OS X. Now we have a tool that runs under Windows. It’s called WinPwn 2.0.
While you can download WinPwn 2.0 from the official site, there is no much information regarding how to use it. I found some tutorials that might be useful.
WinPwn 2.0 Tutorial