The presenter of this tutorial demonstrates how to unlock an iPhone 3G or 3GS using blacksn0w firmware 3.1.2, so you can use it with any mobile carrier company that you want. The tutorial includes 3 main steps: (1) click on the black icon that was added by Blacksn0w software, (2) install "snow", (3) insert your SIM card, and wait. After a minute or so, the presenter shows that that his mobile carrier company is presented as the current carrier and cellular/Wi-Fi supplier.
Blacksn0w is related to Blackra1n by geohot and includes more applications besides Snow such as Cydia (Cydia?) and Rock, which the presenter doesn't mention.
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