The best thing to do is use VirtualDub
(MPEG version), because you can browse video frame by frame. ON one of the dropdown menus (FILE, EDIT, etc) is an option to copy source frame to clipboard. Then you would open Photoshop, create a new file (size is already fine), and paste that frame. Resize to a 4:3 res, like 400x300, 720x540, 640x480 or 512x384. Do it one larger than you want the final to be. Then you can crop about 7% off each side, to make up for overscan, so your screen cap shows exactly what appears on screen and nothing more. Finally, downsize that to a 4:3 resolution. If you did not crop to a perfect 4:3 again, just pick the smallest side and res that. Go to the canvas size, and crop the other side down.
I can create a tutorial for this, but that's the text version.
This is how screen caps are professionally done. The next step, if you wanted to print these on paper, would be to use a fractal up-resolution.
/// TUTORIAL ADDED: http://www.digitalfaq.com/forum/show...reen-1146.html