I found a used dell monitor. When I plug my vga cable in the monitor, i get a message saying cannot display this video mode. I have another monitor and the vga cable works fine with it and the used monitor only has a VGA port. Please help me. Thank Yoy
VGA is an analog signal, so for the monitor to generate the proper image, it needs to apply that signal to the proper number of vertical and horizontal scans per second. Unfortunately, not all monitors support all scan rates. You will get that message when you're trying to drive the monitor at a scan rate it's incapable of.
Are you sure you have the proper resolution for the monitor? Search online for the native resolution of that particular model Dell monitor. Then set your Windows resolution to that resolution.
If that doesn't work, you can try searching for and installing drivers for that particular monitor. These aren't really drivers, but they're a list of scan rates the monitor supports so Windows can offer the proper supported resolutions and refresh rates.
If it still doesn't work, then the monitor is probably broken. It's not unheard of for the scan or sync electronics in older monitors to go bad.