i had that problem when i 1st installed linux but someone on these forums told me how to fix it like this;
as root do this:
cp /etc/X11/XF86Config /etc/X11/XF86Config.bak
pico /etc/X11/XF86Config (careful pico tends to break lines improperly)
scroll to Section "Screen"
remove all resolutions you don't want. I leave only 1024x768 there.
logout, restart X or reboot
the thing where you scroll around a desktop is called a 'virtual desktop' i think, just for refernce.
mmm. this will make things the way they're meant to be. enjoy!