Last month, the Dev-Team released the PwnageTool 3.1 to jailbreak iPhone 2G and 3G 3.1 firmware. But it works only on Mac OS X and not in Windows. So here is a guide to Jailbreak iPhone 2G/3G 3.1 Firmware in Windows.
1. Since you’re using an iPhone, you might have iTunes. But if you don’t have , then download iTunes 9 and install it.
2. Now download the custom iPhone 2G/3G 3.1 firmware parts with the links given below.
3. Now unite all the parts separately for iPhone 2G and 3G using HJSplit.
5. Uncompress the two archives.
6. Open iTunes 9.
7. With the help of data cable, connect your iPhone to the PC.
8. From the Devices menu on the left, select your iPhone.
9. Hold Shift and click on ‘ Restore ‘ and select the custom IPSW file from the uncompressed archives (If it is iPhone 2G, then select its IPSW file and if it is 3G, then select its corresponding file).
10. Now the installation process starts.
That’s all! Your iPhone 2G/3G will now be jailbroken in Windows.
If you want to use other SIM cards in your iPhone 3G, (Not in iPhone 2G since it need not be unlocked) other than AT&T, you have to unlock it. How to unlock your iPhone 3G 3.1 Firmware with Ultrasnow