vista x64 wmp doesn't stop screen from turning off

Hi,

I have Vista x64 fully updated, and when I play DVDs or AVIs in WMP 11 the screen turns off after 20 minutes. 20 minutes is set in power management, but I have WMP "Allow Screen Saver during Playback" unchecked. Why does my screen turn off??

Thank you,
nachum

I figured out the problem.
ionipti: Downloaded NVIDIA driver? Screensaver may still turn on when playing a movie in full screen