If you are Windows 7 Users than here is new Trick for you which help you to Unlock Windows 7 Hidden Themes & Wallpapers. At the time of installation if you choose English (United States) for your time and currency format, for example, the available desktop backgrounds and themes will include a United States section [...]

First you havr to Jailbreak your iPhone 3.1, here is the Tutorial, After that to unlock iPhone 3.1, you must create a custom firmware that uses the current baseband. The iPhone 3.1 update updates the baseband to a newer one that permanently blocks the software unlock.
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