WinPwn
From The iPhone Wiki
The Windows version of PwnageTool, by cmw. WinPwn, QuickPwn, XPwn and PwnageTool are currently the only programs capable of jailbreaking 2.0 firmware.
This software is now discontinued, although there is a rumour of a WinPwn 4.0, but this is unknown if true.
See Sn0wbreeze for a *possible* WinPwn replacement.
