Update : The latest version of Redsn0w (Windows) can enable that tricky DFU mode on Windows! Macs can use the Pwnage tool to create the custom firmware itself…
Warning : This isn’t for the faint of heart. I did not post a detailed writeup cos’ DFU mode is kinda tricky on this one. If you know what this is and what it means, go ahead and try this. All others, please wait while other Windows users verify this.

The links are all interchangeable and you have all the mirrors you can ever …

Update : The latest version of Redsn0w (Windows) can enable that tricky DFU mode on Windows! Macs can use the Pwnage tool to create the custom firmware itself…
Warning : This isn’t for the faint of heart. I did not post a detailed writeup cos’ DFU mode is kinda tricky on this one. If you know what this is and what it means, go ahead and try this. All others, please wait while other Windows users verify this.

The links are all interchangeable and you have all the mirrors you can ever think …

CAUTION : iOS 4 jailbreak is way complicated unlike other jailbreaks. Please proceed with caution.
Requirements :

Jailbroken iPhone 3GS with older bootrom.
You haven’t used Spirit jailbreak before (for untethered jailbreak).
You have Windows (PC). For Mac, try Pwnage instead.
Please read the above requirements again.

More info about these custom firmware files :

[UPDATE] : You need to download files from either step 1a or 1b depending on your baseband preference. Both are unlockable, so I would go with step 1b which is the latest baseband which supposedly does better with the battery. step 1b …

If you get a 1600 or 16xx error while trying to restore to a custom 3.1 firmware for iPhone 2G or 3G, try the following :
Try this first instead of entering DFU mode…for 3G
1)UNPLUG ur iphone and turn off
2)Open itunes
3) hold home as u plug in iphone and keep holding until u see itunes logo on ur iphone
4) then SHIFT+restore and locate the custom ipsw
and there u go! (thanks txccu2000).
If that didn’t work, then try the following :

Try rebooting both iPhone and PC/Mac.
Make sure the iPhone is in DFU mode.
On …

UPDATE : A new version of custom firmware 3.1 for iPhone 2G/3G/3GS is now available here!
Free your iPhone 3G 3.0 from Apple’s chain by jailbreaking your iPhone which provides you with various customization features and even unlock feature which Apple and your official carrier hate! There are various options available to achieve this level of customization on your iPhone such as download firmware files, bootloader files, jailbreak/unlock tools such as Redsn0w/Pwnage or QuickPwn.

If you are not the one to download all the various files and just want the ultimate result, …

Those of you who want iPhone 3G 2.2.1 firmware with 2.28 Baseband and Cydia, download both the files below and join them using hj split.This works both on Windows and Mac. 2.2.1 may not be an important upgrade but it definitely puts and end to accidental upgrades to 2.30 baseband.

Please make sure your iPhone 3G is already pwned (you should have Cydia installed!).
Launch iTunes (Windows or Mac) and restore your iPhone to the downloaded Custom Firmware. (Hold Shift key (Windows) / Opt key (Mac) whle hitting the restore button in …