Sony Computer randomly changing brightness.

I got a Sony Computer about a year ago and it's been randomly changing my brightness out of no where. Generally it moves it two below whatever I set it as and then changes it back to whatever I have set it on.

I have tried doing everything I can think of to fix it. I changed my brightness to whatever it was changing it to, figuring that would work. It would do the same thing with the new brightness (unless it was a low brightness, then it would bring it up). I thought it might be the Adaptive Brightness thing new computers come with, but mine was off! I turned it on and it stopped doing it for about ten minutes, but then continued doing it.

My computer is a Sony VAIO computer, running Windows 7 Home Premium.

I guess I should add on that when it changes to the lower/higher setting it slowly goes back to what I have it set as. Like it'll fade back to the lower light, or slowly brighten to the higher lighting.

This is annoying my greatly, even though it shouldn't be incredibly noticeable. I tried changing to different power plans to change it, but nothing is working. :/

Any ideas?

I think your problem is maybe related to the Sony software overriding Windows 7 power plan settings for adaptive brightness. I don't have the details of Sony's preloaded utilities (like power/energy management or similar software) on your computer, but you can check out them all and see if there's an option for adaptive brightness.