Apple System Profiler may show several USB buses that your computer doesn't have and you can't use. This does not indicate a hardware issue with your computer
This can happen on Power Mac G5 or PowerBook G4 (12-inch DVI) computers. This is a cosmetic issue you can safely ignore. It does not indicate any issue with the computer or Mac OS.
This document will be updated as more information becomes available.
Additional information
The PowerBook G4 (12-inch DVI) computer has two external USB 2.0 ports. The Power Mac G5 computer has three external USB 2.0 ports: two on the back, and one on the front of the enclosure.