Dvd burning problem.. 1 gb movie uses a 4 gb dvd

Hi all, newbie at burning dvd. I have burned some dvds, some are around 1 gb, but when I burn them and have windows dvd marker encode the avi files it takes up the whole 4 gb dvd. They are burned at 16x. So I am sure I am doing something wrong. Below is what very thing is set at, and the programs I am presently using.

When I burn a down loaded torrent, some time I need to convert the files so I use Format Factory, once this conversion is done I burn and encode them using Windows DVD Maker, dvd aspect ratio of 4:3, DVD burner speed: Fastest, AVI Decompressor is check (turned on)

So I figure I best learn how to burn first, befire I learn to rip and ipload some movies.

This is a great site, hope to be able to contribute to it in the near future.

den sirden1959