1901FP resolution problem

I have a 19" 1901FP monitor running on a Dimension 8300 with XP Media Center OS and an All-In-Wonder Radeon MP TV Tuner/Graphics card.  The signal source to the tuner card is the S-Video output from my DirecTV set-top box.  My problem is poor resolution - not only at full screen, but even at smaller image sizes.  The same problem (poor/blurry resolution) also occurs when I play DVDs - so it's not the video source.  I've played with the resolution settings under Control Panel, but nothing seems to help.

I can view the video on the "monitor adjustment" setup screen (the people playing pool) perfectly - the picture is crisp and clear.  What adjustments to I need to make to get the same picture quality on DVDs and TV signal?