@Satan phil,
There are numerous approaches to the infinate regress problem, one such is proofs, in which you can't really provide any more explaination than you have already given. Then again you could always ask why proofs do this, and then your back to square 1. The way I deal with it is basically not to and not to see it as a problem but actually as a solution in itself. Basically, trying to find the
Ultimate Answer To Life The Universe And Everything, is the equivalent of trying to find the maximum or minimum number, this is of course impossible. If you ask a stupid and meaningless question like "what is the answer to life the universe and everything" you will of course get a meaningless and stupid answer like "42", (those who know the Hitchhikers Guide know what I'm talking about). In fact I am prepaired to bet good money that if you ask enough questions you will eventually start asking the same questions more than once, in other words, the whole of reality is one gargantuan circular argument. But this is, in itself the answer I think, for I believe the goal is not in the finding but in the search, the journey not the destination. Life, philosophically and biologically and is largely associated with the idea of "continuation", hence you survive as long as possible and pass on your genes so they continue to exist. I think therefore, the most important "if not the ultimate" answer to life the universe and everything is to:
Keep Going!