2 Movies on one DVD

[iceakacrazydog]

Hello.. I had setup that I could burn 2 two hour movies on one DVD 4.7GB

now setup new PC for games and Video editiong..

I use showbiz to make .avi or so on. to make .MPG and put it on DVD
now one File takes up more then 4.7GB on DVD in DVD moviefactory ...
anyone know what am I doing wrong?

thanks upfront..
(newbie)