I have a flatscreen HP monitor that is only 3 or 4 years old. It has never been moved, bumped, pierced, wet or damaged in any way. It is never left on and has always had the screensaver activated since day. We have no children in the house and I am the only user on this computer. Two days ago, what appeared to be a small black tree appeared at the bottom of the screen. I turned off the screen, then tried restarting the computer and it slowly started filling in to form a round ball. I measured it yesterday and it was 1-1/4" in diameter, perfectly round. Today it is 1-1/2" in diameter. What is happening to my monitor?

It is failing. It isn't the display led's that are failing, but likely the underlying electronics such as capacitors or scan chips. Time to send it in for repair.

FWIW, I have 2 Dell 24" (1920x1600) monitors that are 7 and 9 years old. So far, no problems with either of them.

Tyvm for your reply rubberman, I suspected as much. Just hoped that someone had a fix that I could try. Thanks for the Dell tip as well.