Windows 7 - internet tv--pixelated picture

I am trying to watch internet TV within Windows Media Center. The TV pictures do not stutter, but they are very pixelated, causing some blurriness. Of course the problem is worse at full screen, but even the little screen is pixelated. I have a tv tuner within my monitor, so I know I can watch HD TV over the air with a very good picture. Also, when trying to stream internet by going directly to the source, I seem to get a much better picture. The resolution within the Media Center is set at the optimum for the monitor.

Can someone suggest a fix for this?

Thank you.

It's not intended to look good full screen or in a large window, but in a small window, like youtube. You can resize the video while playing it - most flashplayer based video is usually ~ 320 x 400 or a bit larger if HD - 'stretching' it makes it look like *&^%.

Then what good is it? Microsoft designed it to full screen just obtain poor results? Makes not sense!

I cannot mitigate the factor "what makes sense". It is what it is.