I just thought to make it all easier on you. Here's a zip with two bats. One for 16:9 and one for 4:3. Unzip it to your desktop. Open both in notepad if your mewig installation is not in c:\program files and edit to correct path. Then save the bat, close notepad, take any divx file and dragndrop it to 16:9 or 4:3 bat. It will make a file with same name +.nokia770.avi at the end to the same location your original avi was in.

Should work like a charm.