Unlock and Jailbreak iPhone 3GS on Windows

Now you can unlock and jailbreak iPhone 3GS running on firmware 3.0 to make it work with any carrier:

Step 1: Now you need to download purplera1n for Windows and you must already have iTunes 8.2 installed.

Step 2: Run the purplera1n app. If you are on Vista, make sure you run it with “Windows XP Compatibility” mode by enabling it from the “Properties” tab.

Step 3: Make sure iTunes 8.2 is running.

Step 4: Click on “make it ra1n”:

Step 5: Let the app do its thing and wait for the phone to automatically reboot.

Step 6: You should now have “Freeze” in the list of applications. Run “Freeze”, download Cydia and let it install it.

Step 7: Finally reboot your iPhone 3GS. Voila! You should now have fully jailbroken and unlocked iPhone 3GS.

Download iTunes 8.2

Source:

http://www.redmondpie.com/how-to-unlock-and-jailbreak-iphone-3gs-on-windows/