Reply #8: I'm no expert. If you've regularly unplugged and replugged the cable into the computer,

[struggle4progress]

you might double-check whether a problem has developed with the cable or the port; same if (for example) you'd tripped over the cable or otherwise yanked it by accident recently. That's probably not the case, but if you haven't checked for basic stuff like that, you should of course check. I've sometimes wasted hours on some stupid junk like that

Could you have a virus? That is, do you regularly run an anti-virus program?

Does the OS have a way to calibrate the display?

There may be lots of possibilities. You may have tried everything sensible already. If not, I'd try what I could do easily, and if that didn't work I'd buy a new (returnable) monitor (or borrow one) and see if that solved the problem. If it doesn't, you'll ask more fun questions, like: Could a BIOS setting be wrong (say, because of a dying battery)? :shrug: But if you, as user, guess it's the monitor, you're probably right.

My "get a new one" comment is based on several miserable experiences with modern electronics: my oven touchpad died, and I spent months trying to find someone to replace it; the upshot was that replacement touchpads cost about 50% of a new oven, had to be ordered from abroad, had no warranty, were non-returnable, and had a high failure rate -- so the repair folk wanted me to buy the replacement pad, cuz they didn't want to take the financial hit if it failed