SOLVED: Dual monitor setup stopped working after upgrading client OS

[snoopyjc]

Hi I'm running W7 as host and W10 and Ubuntu as 2 guests. Virtualbox 6.0.4. I have dual monitor setup on host, and I used to have it on W10. I recently upgraded W10 and in doing so, had to extend the C drive space. After the W10 windows update, I am no longer seeing dual monitors. I tried setting Oracle VM back to 1 monitor and then back to 2 and that didn't fix the problem. Display settings: 128MB video memory, 2 screens, VBoxSVGA graphics controller, Remote, recording, and acceleration all disabled.

What is happening is that only 1 screen is opening and it says "Windows 10 (Snapshot 4) [Running] - Oracle VM VirtualBox: 1" for the title. There is no window open that says ": 2" at the end. Here is the logfile (attached). The guest OS is seeing 2 monitors, but the Detect button says "Didn't detect another display.". The "Identify" button shows a big "1" in the (only) display window. I tried looking around and using ALT-TAB to find the second window and it doesn't exist. If I minimize the window and right-click in the tray, it doesn't show a second window. Right-CTRL-f does enlarge the single window to full-screen on one monitor, but the second window is completely missing!

Notes: I recently added the Ubuntu guest OS (just before upgrading the W10 client). I have ubuntu set to 1 monitor - just now I tried setting it to dual monitors and it does the same thing as W10 - it only shows me 1 window. I tried rebooting the W7 host. I tried re-installing the extension pack and also I re-installed VBoxGuestAdditions_6.0.4.iso on the guest W10 OS.

How do I get the second window to show up?

[snoopyjc]

I tried upgrading to the latest version of VirtualBox 6.1 to see if that was the problem. Not only didn't it fix my problem, but it caused several BSOD on my host W7 operating system with:

The computer has rebooted from a bugcheck.  The bugcheck was: 0x000000ca (0x0000000000000002, 0xfffffa8014d5dc50, 0x0000000000000000, 0x0000000000000000). A dump was saved in: C:\Windows\MEMORY.DMP. Report Id: 111420-99388-01.

The BSOD said something about a bad driver. I reinstalled VirtualBox 6.0.4.

[snoopyjc]

Ok - I finally figured it out - I had to check a box!!! (Not sure how it got unchecked, and I didn't know it was there):

VirtualBoxSecondMonitorEnable.png (62.1 KiB) Viewed 2991 times

[scottgus1]

Glad you kept pressing on for a solution!

I saw this but frankly I couldn't remember what to do about it.

[snoopyjc]

Glad you kept pressing on for a solution!

I saw this but frankly I couldn't remember what to do about it.

Yeah I don't quite understand why that option is there. If I only wanted to use 1 monitor, I could have just changed the slider back to 1. What is the purpose of an Enable checkbox on the second monitor, plus I never unchecked it (at least not on purpose)!!??
--joe

[fth0]

What is the purpose of an Enable checkbox on the second monitor

It's simply the equivalent to the on/off switch of a physical monitor. I'll give you a real world example:

At work, I have a Linux PC with two monitors. In the Linux graphical desktop, I use about 10 virtual desktops (not VMs), and on one of them a VirtualBox Windows VM is running and using the two monitors. At home, I have an iMac with only one monitor, and use a Remote Desktop solution to connect to my work PC. When changing place between work and home, I can use the checkbox to turn the second monitor on or off while the VM keeps running.

[snoopyjc]

What is the purpose of an Enable checkbox on the second monitor

It's simply the equivalent to the on/off switch of a physical monitor. I'll give you a real world example:

At work, I have a Linux PC with two monitors. In the Linux graphical desktop, I use about 10 virtual desktops (not VMs), and on one of them a VirtualBox Windows VM is running and using the two monitors. At home, I have an iMac with only one monitor, and use a Remote Desktop solution to connect to my work PC. When changing place between work and home, I can use the checkbox to turn the second monitor on or off while the VM keeps running.

Ok - thanks! As you see, it can cause some issues too, so it's good to see it has a legitimate use!