If you use VMWare on a widescreen-display, you probably know the problem that you can't select your correct resolution in the screen-properties dialog-box.
Simple solution: edit your .vmx-file and add the following lines (edit the values with the resolution of your display):
svga.maxWidth = "1280"
svga.maxHeight = "800"
Boot your virtual box as usual and select the correct resolution in the screen properties.