What is a Mesa driver
 

I have an ATI video card, but it's using a Mesa video driver. What is that and is there anyway to adjust it? Thanks.

mesa is a software implementation of OpenGL. being software it's slow and generally undesirable if you have a hardware alternative. if you install the ati fglrx drivers drivers from ati then you'll be able to hook into the hardware stuff simply.

Just As acid kewpie said.

If you are unintentionally using Mesa, then it's only because your video drivers weren't properly installed. Google for a how-to because the process of setting up fglrx (propietary) or radeon (open source) tends to differ from one distribution to another.