There is supposed to be a windows version of pwnagetool coming for windows. Seems musclenerd and ih8sn0w had a "handbags" moment!

Anyway, there is a new version of redsnow out (mac and windows) which you can use to put your device into DFU mode with geohot pwn exploit applied. You then just need a nice friend with a MAC to supply you with the custom firmware and you are done!

PM me with your requirements and email address, if you need custom firmware I'll send it over.