Screen menu out of control

[fpb]

I don't really understand what is going on here. All I can say is that the menu for my computer screen - I mean, the one that should only start when you press one of the buttons on the screen itself - seems out of control. Most of the time, the signal for brightness appears at the centre of the screen, set at 100 (maximum). This happens as long as the computer is on, and there is nothing I seem able to do to remove it. So far as I can see, the screen software seems under the impression that it is being commanded - continuously - to increase screen brightness; on a few occasion, I have managed to briefly alter the image to "auto correct" (I think), screen brightness has fallen, and then the "brightness" dialog reappeared and swiftly climbed back to 100, screen brightness increasing correspondingly. In theory, to have a small area in the centre of the screen that does not do what I want might not be much loss; in practice, I am going mad. If anyone can tell me how to straighten out this crap, I would be very grateful; my current idea of ripping the screen from the machine and doing a Russian dance on it is, I admit, a bit short on subtlety.

My system is Windows Vista, my screen is Samsung SyncMaster 720n.