Computer Too Dark?

My computer is too dark. This happened all of a sudden about a year ago and I've been trying to find an answer ever since. I've tried other monitors, including one at a computer repair place. Same problem. Replaced video drivers. Same. Replaced video card with new. Same. Tried Hewlett Packard web site. No help. The same thing also happened to my wife's computer, also a HP. Have tried changing brightness and color settings on both. No luck. Have run hardware tests and everything checks out. Any suggestions?|||Have you upgraded direct x ?