At start-up of a computer apparatus, a CPU executes a first initialization procedure included in a RAS module to initialize resources to be used by the RAS module. After execution of the first initialization procedure, the CPU executes an initialization procedure included in an OS to initialize resources to be used by the OS. After execution of the initialization procedure, the CPU executes a second initialization procedure included in the RAS module to copy an interrupt determining part included in the OS to the RAS module, and to set the interrupt detection unit such that upon detecting an interrupt the interrupt detection unit calls an interrupt determining part copied to the RAS module, instead of the interrupt determining part in the OS.