The Dev Team has now released QuickPwn 2.1, which will jailbreak firmware 2.1 using Windows. This latest version will jailbreak and unlock 1st generation phones running 2.1. For 3G phones it will only jailbreak.

You can download from here:

http://84.94.229.115/QuickPwn21-1.zip

http://apt.eggy.cc/stuff/files/windows/QuickPwn21-1.zip