I watch a lot of TV on my computer monitor. To date I have been using Windows Media Player (though I have VLC media player, which I mostly prefer), solely for the reason that it has a nice black frame around the viewing area. When I use VLC, I have to enlarge the actual video area (leading to pixellation!) if I wanted VLC to take up the entire screen.
Why do I want my whole screen taken up with the media player? Because of all that stuff on my desktop (icons, stickies, background picture) that otherwise shows up when my applications are minimised.
I have found a little (free of course!) application that will tidy it all up for me: it is called Clutter Cloak and will black out the entire desktop except for the current video/picture or current application (depending on which hotkeys you use).
This is great for watching movies, looking at photo galleries, and also when needing to take screenshots of a particular application, if you want to include parts of the (black) desktop.
The web site will tell you how to use it, give you screenshots and point you to the download - which is tiny. I found the default settings didn't work for me and I had to change the Ctrl+Alt+F11 keyboard shortcut for photos/video to Ctrl+Alt+F10 (and therefore changed the others too for the sake of consistency).
Now I can use VLC, press Ctrl+Alt+F10 and have a lovely black screen with the video in it. Fantastic! :-)