Virtual Box virtual machine guest OS screen is not resizing in Windows 10

Question

I have guest additions installed on my Virtual Box, so that the screen is a decent size. When I start Virtual Box, the screen resizes properly. I am running Mac OS X 10.11 (El Capitan), the guest OS is Windows 10, and the Virtual Box version is 4.3.30.

However, when I am inactive in Virtual Box, it goes into some kind of sleep mode and the screen turns black. Also, the screen goes back to the small size. When I move the mouse to wake it up, the screen does not resize back to the larger full screen. The only way I’ve been able to get it to resize is to restart Virtual Box.

How do I get it to resize without having to restart?

Answer 1

The screen going black is probably sleep mode, which can be disabled in the Windows power options control panel... Because sleep mode relies on a lot of "hacks" to save power, its probably not playing nicely with VirtualBox's virtual hardware.

Also, its of no useful value to sleep a VM at the OS level -- if you want to do that, use the built in Suspend function in VirtualBox (which actually works much like Hibernate mode) and you get the added benefit of no memory overhead while the VM is suspended.