So, maybe you’re like me and are a big fan of old school games. And perhaps you’ve recently seen one of your childhood’s favorite games on sale on GOG and want to play it for nostalgia’s sake. But if you own a Mac or are running Linux and the game is exclusively Windows compatible, you know that you can circumvent that by installing Windows 10 on a VirtualBox VM.

The Zeus + Poseidon game (aka Acropolis)
Picture courtesy of the GOG website (

Shoutout to my boys Zeus & Poseidon. The game Acropolis, released in 2000, was one of my favorite strategy games besides the Age of Empire series.  

If everything goes as planned, you will have an up and running Windows 10 operating system running on your macOS Catalina or favorite Linux OS. However, as all tech-related things are, virtual machines can be finicky, and you might have to fix your VirtualBox Windows 10 screen size. Indeed, out of the box, your screen resolution and size might look something like this.

The standard VirtualBox Windows 10 VM out-of-the-box, in all its glory.
The standard VirtualBox Windows 10 VM out-of-the-box, in all its (pint-size) glory.

Or something like this, when fullscreen.

The Windows 10 virtual machine when in fullscreen mode.
What is this, a VM for ants?

If your VirtualBox Windows 10 host machine is the size of a postcard, do not panic. Follow these steps to fix your VirtualBox Windows 10 screen size from macOS quickly. 

  • Before anything else, make sure that your Windows 10 VirtualBox host machine has enough allocated video memory. To verify this, follow these steps:
    • Make sure that your Windows 10 VirtualBox session isn’t currently running. 
    • In the main VirtualBox menu, right-click on your machine, then click on “settings.”
Checking your Windows 10 settings.
  • Click on “display” and make sure that your video memory is set to at least 64 MB (ideally, it should be at 128 MB). 
Checking the allocated video memory of your VirtualBox Windows 10 virtual machine.
  • As you can see from the screenshot above, you cannot change your video memory once you have configured the host machine for the first time. If you know that you have insufficient video memory, the best would be to scrap the VM and create a brand new one, making sure to allocate 64 or 128 MB of video memory to your Windows 10 OS. 
  • Once that you’ve confirmed that your host machine has enough video memory to allow for adequate screen resolution and display performance, start your Windows 10 session.
  • In the VirtualBox VM menu, click on Devices, then on “Insert Guest Additions CD Image…”
By clicking on Insert Guest Addition CD Image, you will begin the installation of the packages needed for the proper screen display of your VirtualBox Windows 10 VM.
  • A “Windows Security” alert should pop up, asking you if you’d like to install the software. Click “Install.” Then, the Guest Addition CD wizard will begin and guide you through the installation process. 
The Windows Security alert - click Install.
Installing the missing VirtualBox Windows 10 VM packages.
  • Once the wizard finishes the installation, you will have to reboot the machine. 
Finishing the installation of the VirtualBox Guest Additions.
The VirtualBox Windows 10 VM rebooting.
  • Tada! You are now the owner of a beautiful Windows 10 VirtualBox host machine with an eye-pleasing screen resolution that automatically adapts to your monitor, filling the entire screen.


For some reason, users report that sometimes nothing happens once you click on the “Insert Guest Additions CD Image…” option in step 3. No need to fret; follow the steps below, which should bypass the issue:

  • In the VirtualBox VM menu, instead of clicking on “Insert Guest Additions CD Image…” in the “Devices” section, hover your mouse over “Optical Drives” and click on “Choose/Create a disk image….”
Manually adding the Guest Addition CD Image.
  • If you are lucky, you will see that the .iso file we are looking for (the Guest Additions CD image) is already there! Click on it, then click on “Choose.” You will then see a “Windows Security” message appearing, asking you to either accept or reject the installation. 
The VBoxGuestAdditions.iso package ensures that your VirtualBox Windows 10 screen size automatically adapts to your monitor.
  • Click on “Install” and follow the steps provided by the Guest Addition CD wizard. Voila! 

If, on the other hand, you see no disc image, stay tuned for a detailed step-by-step tutorial on how to install the VirtualBox Guest Addition CD image on macOS manually.

Owner and content creator behind Geeky girl and blogger based in Montreal, Canada. Chocolate and nature lover (in that order). View all posts by Larryssa →

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