Windows users are now able to jailbreak their iPhone 4 (and 3GS, iPod Touch 3G/4G and iPad) using Greenpois0n.
You can download the application by clicking here, it’s a zip file and it’s only about 62kb, which will take a matter of seconds to download.
Once you’ve downloaded and extracted the software, you can run the .exe file and it will prompt you to connect and turn off your device. This is then followed by 3 instructions, which are easy to follow.
Here’s a video to assist you:
Please note: If you have updated your firmware without ensuring that the modem firmware wasn’t updated, you’ll be running modem firmware (Settings > General > About) 02.010.04, which means that this unlock will not work for you.
An unlock for baseband 02.10.04 – 05.15.01 will be released in the next few weeks, the unlock is called LimeSn0w, keep posted to hear about the release!