The Microsoft base display driver on an x86 would only give me 1024 by 768 in 4:3 ratio. Advice on the forums was very specific:
“If you try installing the guest additions without 3D acceleration first and enable it afterwards, you have to reset/reinstall Windows 10, otherwise the installation routine will be broken because of the first crash and it will not work.”
…but actually wrong, as a couple of attempts proved.
Running the Guest Additions installer crashes out at the graphics driver stage every time. Attempting to install the Guest Additions without enabling 3D acceleration scrambled the display, but I was able to rectify it by running:
After chasing contradictory advice from various forum posts I finally hit a combination of actions that finally gave me a full screen Windows 10 desktop in 16:9 widescreen. Depending on your native display hardware and the version of VirtualBox you use, some or all of these may be needed to get things to work.
The installer crash is due to a compatibility issue with Windows 10. Changing the compatibility mode in VirtualBox to Windows 8 allows the installer to execute:
- Open the Guest Additions CD image in File Explorer
- Right click on the corresponding exe file ( 32bit or 64bit) for the installer,
- Go to Properties, then the Compatibility tab, select Windows 8 then press Apply.
This will get the Guest Additions installer to run all the component parts including the graphics installer, although it still didn’t give me a decent resolution.
My final workaround involved the following steps:
- Shut down the Windows 10 guest; enable 3D in display settings, up the graphics memory to 256MB; then restart the Windows 10 guest.
- Mount the Guest Additions CD.
- Extract the drivers manually to the guest hard drive, by running:
- VBoxWindowsAdditions-amd-x64 /extract /D=C:\Drivers
- Right-click on the desktop, from the context menu choose Display Settings, then at the bottom of the Display tab, select Advanced Display Settings. At the bottom of this window, select Display Adapter Properties. In this next pop-up window, from the Adapter tab, select Properties. This opens yet another window for Display Adapter Properties, from the Driver tab, select Update Driver.
- In the next window, select Browse my computer for driver software. Navigate to the Drivers folder you just created.
- You can then choose from Windows 7, Windows 8 and Windows WDDM which is the VirtualBox video drivers for 7/Vista; it’s not great for performance but it does give you a full-width desktop.
- Choosing the WDDM didn’t at first appear to work; it needed a restart (it is Windows after all), after which it gave me a sensible 1366 x 768 resolution in full screen mode.
UPDATE: Since I compiled these notes in the Technical Preview edition, Windows 10 has since stabilised it’s default graphics drivers AND the Oracle VirtualBox software has also improved graphics support for Windows 10, so for the most part you should get a decent desktop resolution. If you do still have compatibility issues, these notes should help you fix them. AJS