well…. I assume they are just backgrounds or you are using highlight layers.
Here is my suggestion
1. Image > Pixel Aspect ratio > Square
2. Resize to 860 X 480 (unconstrain proportions)
3. Set Crop Tool to 640 px by 480 px and Crop part you want to keeo
If your DVD program recognize square pixels…. bring in as is
If not..
4. Resize to 720 X 480 (distort)
5. Image > PAR. NTSC (.9)
Richard M. Harrington, PMP
Author: Photoshop CS for Nonlinear Editors, Understanding Adobe Photoshop, and ATS:iWork