I noticed that I can change the image size of my exported file. I imported a 720 x 480 DV file into CS5.5. I went to my program sequence window and changed the settings to show the smallest image in that window. I then clicked on the image and used the handles that appear to make that small image large enough to nearly fill the screen. When I exported my final file and played the resulting WMV, the image on my screen was nearly twice as large as it would have been if I had not previously altered the image size in the program sequence window. I had to do this alteration for each clip in my timeline, or the unaltered ones would stay at the smaller size. The quality did not seem to be significantly impaired. I learned about this on a youtube video. The person who did the video claimed that this was a simple and quick way to upgrade standard video to HD. Of course this is not true. He was only changing the size of the resulting video. Does anyone know what is really happing when you do this procedure and why it changes the size of the exported video?
The size (resolution) of the exported video is not affected by anything you do while editing. It is dependant solely on the resolution set in the export settings.
Ideally you want to edit in an sequence that matches your media\, which will be the same size or larger than the required export. In other words, the same or smaller is OK. Making things bigger in post is not the best option. If you need things bigger, shoot them bigger.