A projector is like another monitor (separate from whatever else you may have connected), so it's settings are not dependent, for example, on the LVDS (laptop LCD) settings, etc.
You want to focus your efforts on the VGA settings, only. If you're using this for movies, etc (especially if you're running with the lid closed), you probably want to disable the LVDS, and run the VGA only.
I little quick search leads me to believe that this projector's native resolution is 800x600 (they are like LCD monitors, in this way...they have a resolution they work best at...this is because they actually have little LCDs inside them to produce the image), so you should set that as your resolution for it. You may need to adjust the refresh, etc (but that's not been an issue for me, in the past).
Another option may be to set it up through PCC, where you can select the monitor type...