Hi i was just wondering is it possible for me to burn multiple DVD rips onto one DVD and watch them on my DVD player? The files are in an avi format does this make a difference?

I almost always put 2 movies on when I burn a DVD. Fits fine if you have low enough of a bitrate. I use DVD Flick:
http://www.dvdflick.net/

Avi2Dvd is great for that. It will also take 2 avi files and strip it into 1 continuous avi file you can convert to a DVD file.
http://www.trustfm.net/divx/SoftwareAvi2Dvd.php

As long as you're using a computer to play your video files, it doesn't really matter how you slice and dice them. You can even play sub-elements of a given project by individual filename.

It only becomes an issue when you want to play them on standalone players, which very often require specific header file(s) to play a given project (e.g. a movie). There are a few that will try to play individual files, but they are usually limited to a single video filetype when you use that approach.

For example, I've got a Polaroid player that will create its own list of and let me select from that list of .mpeg files. But if I instead provide a bunch of separate .wmv, .avi, etc. files, it doesn't know what to do with them. But, it will list the .mpeg files and let me choose which one to play, play them in sequence, etc.