What you will need:
-iPhone 3GS with Firmware 3.0
-Windows XP/Vista 32-Bit (Vista must be used in Windows XP compatibility mode, Windows 7 not supported)
-A WiFi or 3G data connection
-The latest version of iTunes
PURPLERAIN software download it here Code RapidShare: 1-CLICK Web hosting - Easy Filehosting
(it is highly recommended that you back up your device via iTunes before you begin the Jailbreak)
The Process: Step 1:
Connect your iPhone 3GS via USB cable to your computer and open the purplera1n.exe file. Step2:
Click the large make it ra1n button
Your iPhone will now be placed in recovery mode. You will see a picture of GeoHot that replaces the regular recovery mode screen.
purplera1n will run and then your device will reboot.
After the iPhone reboots, you will have an icon on your homescreen named “Freeze” Step 4:
The “Freeze” app will open and display “Install Cydia” at the bottom of the screen. Touch the button and Cydia will download, unpack ,and install! Step 5:
When the screen displays “Finished!” you can click the home button and return to the homescreen. Your device is now equipped with Cydia and JailBroken!
-if Cydia does not show up after running “Freeze” reboot your device.
-Winterboad is currently not supported as patches still need to be finished. If you install it, it will just crash everytime you open it.
Thanks to GeoHot, ChronicDev, Kroo, Saurik for making this possible!
Now for the unlock
Open Cydia on your Iphone, (you need a wifi connection or 3G or edge).
Let it load completely.
Go to manage--->sources---->edit (top right)--->Add (top left)
Now search in cydia for ultrasn0w
Install it, once installed reboot your Iphone
Now you can call since your 3gs with OS 3.0 is unlocked!!!!