Download Latest Quick Pwn tool 2.2
http://www.zshare.net/download/51721230fe4b9459/

Download a little add on for Quick Pwn tool “BL-39” & “BL-46”
http://iphonefreakz.com/firmware/BL-39.bin
http://iphonefreakz.com/firmware/BL-46.bin

Download iPhone latest Firmware 2.2 for iPhone 2G
http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone/061-5779.20081120.Pt5yH/iPhone1,1_2.2_5G77_Restore.ipsw

following 3 easy steps.
1) BACKUP you iPhone so that you don’t loose any data.

2) Upgrade your firmware 2.2 by using itunes from your computer .

a. Connect your iPhone 3G to your computer via USB cable and launch iTunes and select your iPhone.
b. Hold the SHIFT key and click the “Restore” button. iTunes will launch a file dialog for you to select the firmware file. Locate the iPhone1,2_2.2_5G77_Restore.ipsw file for firmware 2.2 that you have downloaded.
c.iTunes will then restore your iPhone with firmware 2.2 which takes sometime, please wait for the process to complete.

3) Use Quick Pwn 2.2 software to unlock your iPhone .

a.Launch QuickPwn from the unzipped folder to start jailbreaking your iPhone.
b.Please ensure that your iPhone is connected to your computer. QuickPwn will automatically detect it and enable the blue arrow button, click it to continue.
c.the pwn2.2 will guide you throught any easy step to unlock your phone
d.at the end you will got your iphone updated to 2.2 and unlocked.