Only video that is originally 720 x 480 stretches the full width of the screen. Regardless of 1080i, or 480i setting.
720 x 480 is the DVD rectangular matrix at which VGA (640 x 480 square pixels) is displayed on a CRT television. By retaining these dimensions for a digital conversion on your computer and then displaying them on CRT, you have already partially done what we have suggested -- partially distorted your movie by changing its aspect ratio. Example:
A normal movie displayed on a square pixel device (e.g., computer monitor or digital TV) is 640 x 480 pixels. If you divide both 640 and 480 by 160, you get the aspect ratio for these dimensions -- 4:3 (or 1.33:1 if you divide 640 by 480 directly). In your case, if you divide 720 by 480 you get your new aspect ratio which would now be 3:2 (or 1.50:1) on a square pixel device. However, you are viewing it on a CRT device which uses rectangular pixels, so the rectangular pixels are displayed at a square pixel equivalent on the order of an 810 pixel screen width or approximately full horizontal screen deflection less the overscan which you wouldn't see in any case.
As mentioned previously, you have two basic options here. Both are supported by TV. The first is to convert your 4:3 aspect ratio files at their original aspect ratio (i.e., at 640 x 480 pixels) and allow TV to display them pillared (i.e. with black bars to right and left of the main display area) or to encode (or re-scale) your files at either 720 x 405 or 640 x 360 pixels at a 16:9 (or 1.78:1) widescreen ratio and let TV scale the file as if it were a regular 4:3 TV broadcast being "stretched" for widescreen display complete with the normal hidden areas of overscan.
