how to get virtualbox to run at 1366×768 or the resolution you need

1. Shutdown VM
2. Navigate to C:\Program Files\Oracle\VirtualBox\
3. Shift + Right-Click > Open command window here
4. Run command VBoxManage.exe setextradata "name of your virtual machine" CustomVideoMode1 1366x768x32
5. Start VM
6. Launch Desktop, Right-Click > Screen Resolution
7. Choose 1366 x 768

enable 3d, 128mb video ram as well!

for 1920x1080p

VBoxManage setextradata “win7-64” VBoxInternal2/EfiGopMode 5

an example:

VBoxManage.exe setextradata “win102019” CustomVideoMode1 1920x1080x32