Within the last week, a small blue box has been coming up in the centre of my computer screen. It appears at random times, often 6 - 8 times in 1 hour and is displayed for anything from 5 seconds to 15 minutes. The box is headed Contrast/Brightness, with 'DCR' beneath the scales. At the bottom of the box is 1 - exit, 2 - select. The mouse pointer does not register within the box area. I have tried numerous buttons controls etc. but nothing affects the box, I have to wait for it to go of it's own accord. Anyone know what it might be? My computer is an older, Packard Bell desktop running Windows 8.