Default mac address

I want to change my mac address on my galaxy W because my router don't recognize my smartphone and i read on the manual that it must to be in a precise range of number, i read the procedure of LG but doesn't work: infact in LG guide say that i must modify one file nvram.txt, but in my Galaxy there are two file aparentely equals in content : nvram_net.txt and nvram_mfg.txt
....who can help me?