Run gconf-editor from the terminal or go to the GNOME menu bar -> Applications -> System Tools -> Configuration Editor
Disable just those icons:
navigate to /apps/nautilus/desktop
uncheck computer_icon_visible
uncheck home_icon_visible
uncheck network_icon_visible
uncheck trash_icon_visible
uncheck
Disable all desktop icons:
navigate to /apps/nautilus/preferences
uncheck show desktop
