[Hampshire] Resize screen in virtaul box

I am running Virtaulbox 3.04 on a windows PC, the guest OS in virtaul box is
Debian testing with XCFE desktop. At the moment when I run the guest OS it runs
in 1280x1024 which is the same as my desktop so I end up having to scroll the
screen. Ideally I would like to reduce the guest OS screen down in size but at
the moment, I am stumped.

I can't find any tools in XCFE to change the screen resolution, I tried dpkg
reconfigure........... and while it goes through and ask about frame buffers
and keyboard type it does not go through in screen resolution settings. Now I
have heard that xorg has chnaged but to what I am not sure so I don't know if I
am looking in the right place. I have checked my xorg.conf and there are no
screen resolution setting in it, so can anybody advise how to chnage the screen
resolution?

Tim