CPU Affinity

There seem to be many ways to set CPU affinity, some permanent and some
transient.

I have a dual core processor and consistently run several concurrent
processes all of which are CPU intensive. After rebooting my system and
starting these processes the affinity of these processes is set to CPU 0.

This behavior leads me to several questions:

A) If the affinity of a process to only one processor does that mean that
it will only run on that processor?

B) If "A" is true, is that a proper default or have I done something to foul
things up?

C) With a multicore processor is there an optimal CPU affinity strategy and,
if such a strategy exists, how can Windows be cajoled to employ it
consistantly?

I really hate to see one core fully saturated and the other unused.