Jailbreak iPhone 3G, iPhone 2G, iPod Touch 2G or iPod Touch 1G (iOS 4.2.1):

1) Download the jailbreaking software.

   For PC users: http://cache.greenpois0n.com/dl/gp_win_rc6.1.zip

   For Mac users: http://cache.greenpois0n.com/dl/gp_mac_rc6_1.zip

2) Turn off your device, plug it into your computer and open the jailbreaking software. Select "No" when it asks if you are jailbreaking an Apple TV.

3) For step 3 read the instructions before attempting to do them as they need to be performed instantly. The jailbreaking software will repeat the same instructions.

   a) Hold the power button for 3 seconds.

   b) While continuing to hold the power button hold the home button for 10 seconds

   c) While continuing to hold the home button release the power button. Continue to hold the home button until the software gives you the option to proceed.

4) Turn on your device and find the "Loader" app. Open it and install Cydia. Once the device reboots you can reopen and delete "Loader".

Below are the pictures for the jailbreak process: 

NOTE: If the jailbreak fails for iPhone 4, iPhone 3GS, iPod Touch 4G, iPod Touch 3G, iPad 1, iPhone 3G, iPhone 2G, iPod Touch 2G, iPod Touch 1GiPhone 3G, iPhone 2G, iPod Touch 2G or iPod Touch 1G owners and you find yourself unable to start your device hold the Power + Home buttons until your device restarts and repeat the instructions given above.