I have a PC that I built and I have both Windows 7 and Ubuntu on it. When I bring it up in Ubuntu both monitors show up and everything is fine. When I bring up Windows7 only the primary monitor is detected. The second does not show up in the CONTROL PANEL/ Appearance / Display.

I conclude that all is connected well and the monitor is connected. Oddly, I don't see anything in the bios to set for display but I suspect that is not relevant as the second monitor shows up just find under Ubuntu.

I've done lots of web searches on this issue and I am coming up with no solutions.

Any suggestions?

That's weird... it works in Ubuntu but no in Windows? At least that means the monitor is connected and powered properly. Have you got Windows to detect the monitore? Then obviously, Extend or Duplicate the display to that monitor.

How is the monitor that won't show connected compared to the one that will? Both on the same video card? Two separate cards? One internal, the other on a card?

I'd say the issue is the Windows driver for whatever video device the nonworking monitor is connected to is faulty/corrupted/outdated/pick one.

One trick is swap the monitors' connections to the PC. Does the working one stop and the other one start? That's proof right there.

Windows and Linux don't do displays the same way, so while you know the hardware works, that proves nothing about your Windows drivers.



The Jedi Master

Yes, both monitors are plugged into the same video card. But Windows 7 does not even detect it. So no way of extending duplicating. After shutting down I have just unplugged the larger primary monitor and started Windows 7 back up and the smaller (secondary) monitor comes on just fine. I have one more experiment I could try and that is switching the ports the cables are coming into. It is an older card so has one HDMI and one DVI input. It would be a hassle to do the switch (long story) but could be done. But I suspect this is some Windows 7 and not a hardware issue as I have no trouble at all when using Ubuntu.

How do they connect to the GPU? DVI on both? One on HDMI?

I've had something similar in the past with my AMD GPUs. Eventually, I got things working just by trying things until I got lucky. Took a while.

In one case, it was "just a setting" in Windows or my Graphics driver software. However, the setting was not obvious to me. And, I don't remember which one it was.

One technique to try (when nothing seems to work) is to do a graphics "reset" -- or clean install. That is, uninstall the graphics drivers completely using Control Panel/Programs and Features. Try to find the graphics driver folder on the C: drive and empty it -- it may have a file with settings in it.

Then, shut down the computer completely. Unplug the PSU for a minute.

Reinstall PSU plug. Start Windows. Download and install the latest WHQL driver for your card (of course, you can download it before doing the above). In effect, you are "starting over" and if all the appropriate folders had been cleared above, you will create new folders with new settings files. Hopefully, if something needs resetting, this may work -- but, it may not.

Sometimes one can find "clean install" software for one's GPU. Either from the maker (e.g. AMD, Nvidia, Sapphire, etc.) or as a "free" app. Need to Google. On Windows 10, AMD drivers will do a clean install for you -- don't know about Windows 7. That could save some time, if it works.

Just something to consider if the problem persists.

The smaller is on a adapter from DVI to HDMI cord and that is plugged in to the HDMI port and lager monitor is DVI to DVI port, both go to the GPU card, not the on board video.

Tried plugging it in to a different DVI port? Or running two DVI-to-DVI cables instead of using HDMI? What GPU is this, btw?

What should not be is, And what is should not be.

Here is the trick that did the solved the issue. I shut down the PC, disconnected the large primary monitor and verified the the secondary was connected. I started up the PC again and the smaller secondary monitor, now being the only monitor, came up with image just fine as expected. Now here is the key. While the PC still on and Windows 7 still up I connected the larger monitor ( now behaving as expected as the secondary monitor) and low and behold. It too now had the images sent from the PC (was not just a black screen). And when going into the control panel and display / adjust resolution both monitors show up.

So, if you ever have this problem and you have verified the monitors work and the cables are all plugged into the video card ports and such the thing to do is start up the PC with it only connected to the monitor having the black screen. It should come up fine. Then, with the PC still on connect the other monitor. It should display just fine.