7900 GS Overlay disabled???

I just put a new system together and have the xfx 7900 GS. The one thing I cannot configure is the overlay settings using the nvidia panel. For the tv and video settings so I can watch movies in a brighter setting. But everytime I try to use it, it tells me the overlay is disabled??? Why is that, I remember my old system had the GE Force 3 and that worked fine, so its been a while since I had a new card. But I don't know whats going on, but if I do adjust the settings, it does change on media player, but when i close the program, the default changes back in the panel and i would have to change it in the nvidia display panel again, can someone please inform me what is going on. Is this because I'm using codecs and divx? Thanks for any help.

This is a brand new system, installed with the latest nvidia driver, and brand new installed into my system. I'm using windows xp sp2, and sometimes it saids disabled, and other times I can try to use it. but it works when media player is on, I can see the difference when I do adjustments. Its just that everything I set the gamma to +15, it goes back to -8 for some reason, and it always does that, I cannot apply my settings and just have them go back to -8 again.