I have VirtualBox 6.0.8 on a Windows 10 x64 host. I created a new Windows 2000 x86 VM, with Guest Additions installed. Video memory is maxed out at 128MB. I tried to increase the VM's resolution to 1024x768, first through the guest OS's Display Properties, then through VirtualBox's View -> Virtual Screen 1 -> Resize to 1024x768, but in both cases the resolution remains stuck at 640x480. Attempting to change via Display Properties gives the following error.
The display control panel is unable to change the display settings. The graphics driver returned an unexpected error.
After some research, I tried reducing the video memory to 64MB, which didn't help, and then to 32MB, which works. The resolution can be changed properly now.
Why is this the case? The only thing I can find is this which only contains a mention of the above solution. No explanations were given. Is this a VirtualBox bug? Or is there some kind of legacy compatibility with Windows 2000, in which case why aren't video memory allocation above 32MB flagged by VirtualBox with a warning?