can't stretch 4:3 aspect ratio video on windows media player?

I just bought a widescreen monitor and other players allow stretching of 4:3
video to fill the whole screen but windows media player does not. So I
usually play other full screen files using other players. But on the internet
when I stream a full screen video there is no way to get around that. I am
very frutstrated. This should be a very very common issue and I can't believe
microsoft hasn't addressed it. Any feedback is appreciated.