Latios said:
Oh. Personal experience -> HP monitors suck. You should send it back to HP if they have that service and get a new monitor. Because really, I don't know how to solve a monitor problem, and I know HP monitors are a bit poorer in quality than others.
Seconded! The hp CRT monitor that came with my current PC started going bad quite a while ago... it was far too dark, even with everything turned up. This monitor I have had since, like, 1998 is still as good as it was the day we got it, and it doesn't even have a brand name.
Replace it with another monitor, if you have one. If you don't, find someone who does, or get a new one. Or you could just check the buttons more carefully, because nothing other than the buttons on your PC can do that.