The disc that my motherboard came with, with drivers and such, wants me to install ATI Catalyst, however I'm using an Nvidia card. Should I install the program and just leave it alone, or not install it at all.
It is only needed by ATI cards as a form of a driver, you do not need it. Don't install it. Plus, it's dumb anyway as you are always better off getting most recent drivers online.
What motherboard do you have exactly? I find it strange that it should come with ATI/AMD drivers unless it's an AMD board. The Catalyst driver does contain some other chipset drivers like RAID/AHCI however.