Two days ago, my monitor suddenly showed "ribbons" of vertical thin, blue/black lines with white hatching here and thereThe ribbons sometimes change couoor or flash. I checked all the connections to and from the monitor with no good result. All the programmes are working as usual, but it is difficult to see the work properly.
As the Monitor is several years old, I thought I must need a new one. Today I bought a new monitor and set ut up, only to find the same problem. Can anyone suggest what is causing this to happen. I must apologise for any spelling errors, as it is hard to see exactly what I have written!

Sadly, you told us nothing of your computer, the make, model, if on-board graphics or card, version of Windows or any thing. So we have basically nothing to go on, except 2 monitors don't work. My guess would be the graphics solution, whether on-board or card. You could try new drivers, but I don't think that is it. Does Safe Mode work properly?

Welcome to D-A-L.

First verify all video cables/connections.

It's either your monitor, or your graphics controller/video card if so equiped.

Once you verify the monitor is OK, if it's "on-board" video, install a graphics card in a mobo slot (if available) or get a new motherboard.

It's either your monitor

He already bought a new monitor so I don't think it would give the same results even if bad right out of the box.

I've seen monitor cables installed "upside down". It is possible.

If a new monitor is installed correctly, then it must be the systems display medium.

Wow! Never seen that with monitors since D-Sub (analog) connectors are trapezoidal in shape, and DVI connectors have a key and a shape similar to a trapezoid but with curved, slanted sides. But of course, these connectors are not very rugged and too much force can damage the connectors, plugs, or pins so certainly care must be taken.

Yes. Some of the pins (on "D" connectors) get bent down when this happens. (No "hole" to receive the pin.) If you're extremely careful bending the pins back up, the connector can be saved.

If you're extremely careful bending the pins back up, the connector can be saved.

Yep. But only once or twice before the pin simply breaks - but then that's pretty much with any pin-type connector. Fortunately, HDMI is replacing DVI as the new standard for cards and monitors, so eventually pins and upside-down insertions will not be a problem.

Thank you all for your suggestions. It was the Graphics Card, which is now replaced and I can see what I am writing! The card and fitting was a lot cheaper than the new monitor would have been, so all is well

You're welcome. Thank you for the follow-up.