2300MP quality problems

Hello. We just bought a 2300MP, and set it up to run a powerpoint slide show, using a PowerBook G4. But the picture quality displayed was really poor. If one looked at the laptop display, the pictures were clear and beautiful. But the projected image was very high contrast and had wrong colors. Places that were so dark, you couldn't make out what it was. We could adjust each and every picture and get a little better quality, but there were 100 pictures, and it seemed to loose the adjustment when it went to the next picture. Finally we hooked another, non-dell projector, and immediately we had a beautiful slide show. What were we doing wrong? Is there a button we should have pushed? We scoured the manual, but could find nothing to help us. Is it just that the projector itself is low quality? Francis