The Code 12 error can be fixed by uninstalling the PCI drivers on your PC. The PCI drivers are associated with the motherboard. An error code is an indicator to a user of a piece of hardware or software that an error has occurred and an identifier regarding the specific error responsible for the problem. The error code 12 occurs when 2 devices installed on your PC are accidentally assigned the same I/O (input/output) ports or the same direct memory access.