Wireless Joint

I've bought the unlocked att mr6500 from amazon, I want to ask about how to unlock the n78 because I'm using in Hong Kong, my firmware just 10.04, I have try to use mrconfig, but I've try many times, it also told methe cmd "mrconfig" is not recognized as an internal or external command, operable ...

Sorry I have a very silly question, I’ve try to use mrconfig, but it everytime just show me ’mrconfig’ is not recognised as an internal or external command, operable program or batch file. How can I fix it?