I have two different copies of a movie from my ReplayTV. One is 352x480 and I have a 20-second clip from the other that has a resolution of 720x480. What is the easiest way to convert the 720x480 down to 352x480?

The reason is that I'm trying to use VideoReDo to combine the pieces. Perhaps there is a better program to do this. They are MPEG's, by the way. Trying to burn them for use on our DVD player.

Thanks for any help you can provide.