This is, of course, one of the Fundamental Questions(tm).
It is often more succinctly stated as, "why is there something instead of nothing?"
However, it's thought-provoking to turn the question on its head: Why would there be "nothing" instead of something? *Can* there be "nothing"? "Nothing" is at best an imaginary abstract concept, but does it, can it, actually reflect any possible mode of reality or existence?
The only state *know* is possible is "something" -- perhaps there is no other possible alternative.
Thanks again.
I picked up a Douglas Adams compendium last weekend, so I now have the answer for all of this.
(shhh....it's 42!)