What HD is my monitor?

Your monitor will support 720p since that means 720 rows of pixels (your monitor has 1050 rows). You can watch HD video on your monitor if it and your video card support HDCP; most modern ones do.

Your monitor is 16:10 aspect ratio (simply divide 1680 by 1050) and you will have black bars when watching a video that is 4:3, 16:9, 2.35:1 aspect ratio. Those are the more common aspect ratios, but there are many more less used aspect ratio for movies.

Video is not always 16:9. See previous post.

The Dark Knight for example is 2:35:1, therefore when watching it on any monitor or HDTV there will always be black bars on top and bottom.

Programs broadcasted in HDTV will usually be 16:9 widescreen format. There will be exceptions like movies or shows that were never in widescreen format like Star Trek: The Net Generation or the earlier seasons of ER to begin with.

hi! I'm thinking of buying a 1080p monitor for my pc, but I don't know what I need for it to be compatible. does my graphics card have to support the 1920×1080 resolution, or is it automatically supported? my card is just a 6800LE, can I connect a 1080p monitor?

It's for watching movies, not for gaming. And by the way: what resolutions does a 1080p monitor support (for in games, my 6800LE is obviously not powerful enough to run a game decently at 1080p, but 1280×1024 or 1024×768 are no problem with the games I play.