If your not certain what your doing here you might want to look at an overview of avi and viewers for different platforms as well as how to set them up.

If you are interested in the most up-to-date viewers and latest/greatest programs available I would suggest the "video" subcategory of the "multimedia & design" category under download.com or shareware.com and search for the word "movie".

If you are using a microsoft windows 95 or windows NT platform and have not yet installed the windows media player it is freely available for download.

If you are using a linux machine and don't already have a viewer I recommend xanim.

If you are using a mac you might want to try the simple image.