I'm having problems burning a dvd.?

hello, i have an lg 20x external super multi dvd rewriter ge20 as my dvd burner and power producer as my burning software. when i download a movie on ares that is only 700mb and only 1 hour and 40 minutes long, and i put it onto power producer, it shows that it is much longer and the full movie doesn't burn onto the dvd, which is 4.7gb big. Compressing and decrypting doesnt work. what is wrong????????????? please help!!!!