26 of 41Image
For this feature to work, Virtual Machine Additions (VMAs) must be installed. Right now, it isn't so this setting is greyed-out (inaccessible for configuration). In the next set of images, we show what the installation of Virtual Machine Additions looks like (it's accessible from the ACTION menu on the main window of any running virtual machine.
For David Berlind's write-up on The Virtual PC 2007 User Interface, see his post in ZDNet's TestBed blog.