possible positions quest

The question is simple.  The solution is not.  How many POSSIBLE position exist after move 5?  NOT PROBABLE positions but POSSIBLE positions.  Of course realizing that specific positions may be reached by multiple combinations makes this a greater challenge, as the question is how many positions not how many series of moves.  So, some of the positions may be reached in a number of ways.  Also, I realize that there are a handful of "book" mates that do not require a full 5 moves to execute.  These should count as a possible position as well I believe, for the sake of this argument, as that number is fairly small anyway. 

We all know that there are 400 possible positions after the 1st move, and then it gets CRAAAZY.

If there is a mathematic formula for knowing this that would suffice as an answer as well, assuming it is accurate enough.

i think the question shuold be phrased this way:how many unique positions can be reached during a game of Chess whose rules are defined by FIDE, USCF or whoever.

OK, that works.  Question posed.  "How many unique positions can be reached during a game of Chess whose rules are defined by FIDE/USCF?"(alison27)