I have a few Lenovo ThinkCentre M73 Tiny form factor desktops that are hooked up to two monitors. One monitor uses the available VGA port and the other uses the available display port. 90% of the time I don't have any problems. Both monitors display and extend as they are supposed to. However, every 3-4 weeks the user will come up to me and say their monitors went black, usually after coming back from lunch.
Sometimes I can unplug both wires, tap the power button, then plug them both back in and tap the desktop power again, and both computers turn on. Often, however, I have to unplug the display port and turn the computer completely off, at which point the computer will display through the VGA only. However, if I plug the display port back in after that it will automatically change the VGA to display 2 and I can see the user's wallpaper but it still thinks the display port monitor is monitor 1 (Even though it's dark) so I can bring up the display properties to change anything.
At first I thought it was just the one computer but I've had it happen to three of them now. Same problems every time. I've changed out the monitors and the wires without success.
Lenovo M73 Tiny form factor
VGA and Display port input available (Works most of the time)
Connected to two monitors of varying sizes (Usually around 19 or 20 inch)
The Display port input is using a direct display port to DVI wire (I've tried cable matters and Amazon) The monitors themselves don't have display port inputs.
Windows 10 Pro
if it was a larger form factor I would just throw a video card in there but there isn't any room for one. I have a few Dell desktops that are the same size but I haven't had this problem with them so it appears to have something to do with these Lenovo's specifically.
Make sure that the Chipset driver is up to date.
Make sure the Video Driver is the newest.
Then, set Power Management so the system is always ON (that is does not suspend).
These things should help