iPhone 3G - iOS 4.0 upgrade

Many out there have been thinking on how to go about the upgrading jailbroken iPhone 3G with iOS 4.0.  Its quite simple and well ensure you make following preparations before going with the upgrade -

1. Back-up your iPhone using iTunes
2. Make sure you have the latest version of iTunes installed, if not please update iTunes first.
3. Download iOS 4.0 from - http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone4/061-7380.20100621,Vfgb5/iPhone3,1_4.0_8A293_Restore.ipsw
4. Download the latest version of RedSn0w from - http://iphwn.org/get/redsn0w_win_0.9.5b5-5.zip (hoping that you using Windows O/S)
5. Ensure that you have WiFi network available - you would require to use WiFi network later to unlock your iPhone.

Now that you are ready follow following steps -

1. Update your iPhone 3G to iOS 4.0 using iTunes
2. Switch off your iPhone (keep it connected to your Computer)
3. Start Redsn0w and point towards the ipsw file you downloaded in step 3 above.
4. Select Install Cydia - you would require this to later unlock your phone to connect to any network
5. Follow Onscreen instruction and let Redsn0w do the needful for jailbreaking your iPhone 3G with iOS 4.0
6. Your phone would reboot once Redsn0w jailbreaks it.

Few things that you need to make note of - when you are using Redsn0w to jailbreak your iPhone 3G with iOS 4.0 -

1. when you start RedSn0w, ensure that the phone is switched off and connected to your machine
2. when prompted on RedSn0w screen, hold power on button for exactly 3 seconds and press Home button immediately
3. Keep Holding Power and Home Buttons for exact 10 seconds
4. Release Power Button and hold Home Button for Next 30 odd seconds till RedSn0W detects your Phone in DFU mode.

Done you ready with a jailborken iPhone 3G with iOS 4.0, now its time to unlock the phone. Follow following steps to unlock ur phone -

1. Connect to the WiFi network and start Cydia that you installed while jailbreaking your iPhone
2. Go to Cydia and add repo666.ultrsn0w.com under Sources, you can do this by selecting Manage->Sources-> Edit
3. Install Ultrasn0W
4. Reboot your Phone
5. Done - Your Phone is Ready to be connected to any network you want.

 Please refer to following for details -
http://www.iphonedownloadblog.com/2010/06/21/jailbreak-iphone-3g-on-ios-4-with-redsn0w/