Answer
ArcView is a single-thread application, therefore it will not take advantage of multiple processors, or CPU's. When ArcView is launched, the operating system selects a CPU on which to run, and all ArcView processes spawned from that initial session will run on the chosen CPU.
Multiple CPU's can be advantageous when running multiple sessions of ArcView at once or if there are several processes running at the same time. The operating system will divide the work load among the various CPU's.