I have a few ideas, since i took a electronics class for a few years, but I couldn't find whats wrong with my computer. I have two computers, a good one, and a bad one, one for school work and important things and one for messing around. A typical set up, as they both run with the same monitor, I switch back and forth with the monitor and other plugs. I have had my old computer for around 12 years, its a Dell, and I have used this monitor on it a lot, before getting my new computer. My monitor works fine on my new computer, but on my old one when i turn the power on, the little light on my monitor (A dell also) remains orange, so if i remove the cord from the back of the PC a message appears on the screen no signal detected, so i plug it back in, and the light goes green, i can hear the monitor sound like its going to do something, and then the light goes orange. I was just using not too long ago around Christmas last, and then i went away a few days and it hasn't worked since. Again, everything is fine and normal on my good computer though and I have used this monitor on my old PC before. I never changed any settings and I'm the only one who uses it. If you need more info let me know and thanks in advance.