Having trouble viewing zoomed video

Can anyone help me on why I get a fuzzy picture when I full screen a video I’m watching. It happens with built in players on websites or sopcast. When I full screen the video it’s a little blurry. I’ve installed all major plug-ins for windows media player but still there is no difference.
Answer #1
And I forgot to add I recently installed windows 7 Ultimate too.
Answer #2
Probably because Sopcast is pretty poor quality video, with a low resolution, and when you maximize it it’s stretching it to the point the software has to “guess” the other pixels.
If you think it’s not that, try enabling hardware support in your video options on Windows Media Player or hardware overlay in VLAN. As for Sopcast, there should be a hardware acceleration option somewhere.