iPhone Dev team had renamed yellowsn0w which was earlier used to unlock iPhone 3G with old firmware models . Yellowsn0w  is now known as Ultrasn0w for all iPhone 3G and iPhone 2G models with iPhone OS 3.0 . Before unlocking iPhone OS 3.0 with Ultrasn0w 0.6 ,we need to jailbreak the phone with PwnageTool or Redsn0w . Redsn0w 0.7.2 can be used in Windows and PwnageTool 3.0 can be used in Mac to jailbreak iPhone OS 3G with OS 3.0 . After jailbreak we can Unlock iPhone 3G with OS 3.0 using Ultrasn0w .

Jailbreak  iPhone 3G with OS 3.0 using Redsn0w 0.7.2 :

Redsn0w 0.7.2 is a multi-platform tool for jailbraking iPhone and iPod with OS 3.0 and to add Cydia installer to work on non app store supported applications . Redsn0w 0.7.2 has a very easy to understand UI than earlier versions .

Download Redsn0w 0.7.2(Windows) .
Download Redsn0w 0.7.2 (Mac)

Download OS 3.0 for iPhone 3G and iPod  and copy it to the unzipped Redsn0w 0.7.2 folder .
Connect  iPhone 3G ,iPhone 2G ,iPod 1G or iPod 2G to iTunes 8.2 .

Now restore the corresponding ipsw by selecting the folder location . Here on restore operation ,hold shift if you are using Windows or in Mac use option .

Now run Redsn0w 0.7.2 >select the ipsw file from copied folder and click next . Opt to install Cydia and continue .Operation will continue in a flow and click on next at suitable events . After finish restart your iPhone 3G or iPod touch with OS 3.0 .

Unlock iPhone 3G with OS 3.0 using Ultrasn0w .

After jailbreaking  OS 3,0 with ,Redsn0w 0.7.2 we can unlock iPhone 3G and iPhone 2G with Ultrasn0w .

Make sure to jailbreak iPhone OS 3.0 with Redsn0w 0.7.2  . Select Cydia installer if you have already jailbreaked your iPhone . First select packages from two options in Cydia , select to edit and enter repo666.ultrasn0w.com as source URL and download Ultrasn0w .

Now return to Cydia sources and select to install Ultrasn0w from the list. Follow Cydia instructions carefully and continue to unlock iPhone with OS 3.0 .

After installation , press home button and tun off iPhone 3G .
Now insert your alternate carrier SIM card and restart phone .

Note :  This is only a news regarding iPhone Dev-Team and their application  to unlock iPhone with OS 3.0 .  iPhone and iPod are registered trade marks of Apple Inc . ,and users generally will have to follow their service agreements while using them . We do not  recommend to unlock iPhone 3G and use it with another carrier . Results cannot be guarantied on trying the above tutorial and we are not responsible for any hardware and software damages thereof .  So we strongly advice you to keep iPhone 3G with existing carrier and enjoy all cool benefits rather trying to unlock it and end up in trouble .