Why does my screen dim on a desktop installation of Windows 7?

Why does my screen dim on a desktop installation of Windows 7? Periodically, while using my Windows 7 Pro desktop installation, the screen suddenly dims. The brightness is about 75% normal (estimate). It's as if I am in a power-saving mode on a laptop running on batteries. But this is a full desktop installation.
Asked by: Guest \| Views: 348

Total answers/comments: 2

Comments display order:

Guest [Entry]

Are you using an NVIDIA card? I am and had the same exact issue on my desktop. I found a solution in the NVIDIA Control Panel (right-click your desktop and select "NVIDIA Control Panel"). Under "Display" on the left-side menu, select "Adjust desktop color setting". On this screen, click "Use NVIDIA settings". My screen brightened up as soon as I selected this.

Guest [Entry]

That sounds suspiciously like what happens when the UAC prompt displays. Are you sure there isn't a dialog in the foreground which asks you whether you want to allow an application to perform an action which requires administrative permissions?