Look into Adobe After Effects - it is resolution independant and will allow you to create a composition at 720x480 import the oversized image and animate it however you like across the "window" of 720x480.
Creating a Flash movie @ 720x480 x 30fps and exporting the movie to a frame sequence will work too. You can then import the frame/animation sequence into Premiere and render it out from the timeline for output to tape.
I have been trying to do exactly the same thing. I have lots of panorama JPEG pictures that I have created using my Canon camera. I want to use them as part of my videos. I only have Premiere 6.5.
Is there any way I can do it ?