Yeah, I agree, look at the drivers first. If you have an integrated ATI or nVidia chipset, you might even find some modified drivers out there, they usually have a plethora of resolution settings.
In case you need to buy a new card, the question is what you're doing with your computer and what the other specs are. If you want high image quality and possibly second monitor, use Windows and don't play games at all, Matrox would be an option. Otherwise probably an entry-level nVidia or an ATI card.