If the “Auto-resize Guest Display” is greyed out for you, go ahead and reboot your virtual machine and check if the issue is resolved. In case that doesn’t work, go ahead and restart your VirtualBox.

I want to convert several pictures taken with a 6MP digicam (2848x2136) in order to fit a 16x9 screen (1280x720p res). Using Irfanview, I've already tried <B>resizing</B> (not cropping) but the image ...