The display at 640 x 480 suggests that it is using a vga plain vanilla
driver. You can try looking for a better one in System, Administration,
Hardware Drivers. You can find out about your drivers by typing lshw in a
terminal and scrolling back through with the mouse to the *-display section.
If you see UNCLAIMED then you have a driver problem. You can copy that
section and post it back to us if you want.