I'm running Windows 10 inside VirtualBox 5.1.18 on OS X 10.11.6 and after installing Guest Additions to enable bidirectional c/p the screen resolution has shrank to 800x600 and I managed to increase it to 1024x768. Even though it brings some memories of the times when I was young and restless it won't allow me to do any serious work in Visual Studio. First time I installed them trough virtual CD-ROM and second time manually by downloading the right version from the official page.
How to: Use 1080p Resolution on Windows 10 Insider Preview - VirtualBox - posted in Windows 10: When you first install the Windows 10 Insider Preview in VirtualBox, it will be stuck using the default resolution. Normally, to use higher resolutions, you could just install the guest editions. Unfortunatley, this does not work on the technical preview. Jun 01, 2015 Hey, I just installed the Windows 10 Preview (64-Version) in Virtual Box on a Windows 7 Pro x64 as host. So far everything is working except the guest additions (which I don't really need). My only problem now is: I can't get it running with my native screen resolution (which is 1920x1200). Windows 10 only lets me select 1600x1200 as maximum.