Tech support: Help with .avi files?

Hi,

Does anyone know anything about manipulating .avi files?

This is academic rather than fannish. I run a computer model that outputs an .avi movie of a changing virtual landscape, but the movie is small and much too fast. The movie is made in Matlab, so help from that direction is also possible, but probably more complicated?

I need a program/instructions on how to:

1. Change the movie's speed so that it will stay slow when opened in powerpoint.
2. Make it larger on the screen, if it that lowers resolution.
3. Crop the movie down to just the animation in the center of the frame. (There's a giant flat gray box around the actual moving picture of my research.)

Can anyone help, please?