Setting up X on an Inspiron 8000

I've got an Inspiron 8000 with an ATI Mobility M4 board inside and I'm trying to get X up and running. Everything works fine, except for the fact that I can't switch resolutions. I can go between 1400x1050 and 1024x768 and that's it. I really need to be able to get down to either 640x480 or 800x600

Setting up X on an Inspiron 8000

I've got an Inspiron 8000 with an ATI Mobility M4 board inside and I'm trying to get X up and running. Everything works fine, except for the fact that I can't switch resolutions. I can go between 1400x1050 and 1024x768 and that's it. I really need to be able to get down to either 640x480 or 800x600