Windows 7: Video playback quality gone horrible!

Hey Arc

Whats the procedure to check if the vdu is over-occupied?

One more thing, earlier when I used to play videos (any format), the Windows used to set the current Aero theme to Windows 7 Basic theme and then the video used to play.
I assumed Windows was trying to optimize its performance.
Now, it plays the video WITHOUT changing the theme.

I tried adjusting the performance settings under Advanced System Settings and also increased the Virtual memory. But no changes.