[Solved] Windows 10 Guest Display Adapter does not support auto-resizing

[OtherPhilC]

I have had several VBOX clients installed for some time on a Windows 7 Ultimate host, originally created on VBOX 4, but now running VBOX 5.1. The host Windows 7 64 bit machine has an Intel Core i5 2500 processor, and dual HD monitors configured as an extended desktop with video supplied by the Core i5 HD graphics. All guests were easily configured, and have no display issues. All processor features are enabled.

The Windows 7 32-bit guest automatically sizes to the full frame of the 2nd monitor. The automatic resolution of the guest is 1920 x 1016. The 1016 vertical value automatically takes the host window frame size into account.

Yesterday I created a new Windows 10 32-bit VBOX guest (new install from ISO, not an upgrade) using "Guided Mode" with all defaults. Windows 10 installed without a hitch. (Windows 10 Professional Version 1511 build 10586.164)

All behaviors of the Win 10 Pro guest appear ok. (Internet access, etc.) However, there is one major problem: I can find no way to enable automatic screen resizing. On the View menu "auto-resize guest display" is greyed out. The only difference I can see to possibly account for this is that instead of installing a "VirtualBox Graphics Adapter" like the Windows 7 guest has, VBOX installed a "Microsoft Basic Display Adapter" into Windows 10. I have no idea whether that choice is "normal" for a Windows 10 guest, but the behavior it has is decidedly different from the Windows 7 guest video adapter. I have searched the forum, and see several posts about Windows 10 graphics, but none seem to address this particular issue.

One other fact: I installed Windows 10 providing a Windows 7 Ultimate key. The key was previously unused and I wanted to upgrade the spare key to Windows 10 before the deadline. The Microsoft iso automatically installed Win 10 Pro with this key, as expected. I include this for completeness.

What must I do to get auto-resizing with full frame of a maximized host window in my Windows 10 guest?

[socratis]

Did you install the Guest Additions in your Windows 10 guest? Take a look at the User Manual for the how-to.

[OtherPhilC]

Never mind. I solved the issue by installing guest additions. Sorry for the false alarm.