Though the Windows version of Pwnage, WinPwn, was originally slated for release shortly after the Mac OS X version became available on April 3rd, WinPwn has nevertheless been released and is now available. The currently available version, 0.99.1.8, is however a beta release and is cautioned by its author to be unstable and for beta testers only.
The WinPwn beta is also lacking 2.0 support, as features related to 2.0 were considered to buggy to include in the beta release. As such, WinPwn requires that testers have their iPhones upgraded to 1.1.4 in order to "pwn" their iPhones or build custom .ipsw files.
A new beta version containing support for iPhone 2.0 is slated for release in the "next few days", according to the WinPwn homepage.WinPwn's author is recommending that all those who intend to download and test/use WinPwn review and follow this tutorial. As with all iPhone third party software, especially jailbreaking/unlocking utilities, proceed on a run at your own risk basis. Installation/use of WinPwn can result in data loss or require you to restore your iPhone.
To download WinPwn, visit the WinPwn homepage.