Spider Solitaire

Recently I have been wasting a lot of time playing the Spider Solitaire game which comes with Microsoft Windows.  Playing the 4 suit version (without using the undo feature) I managed to win 37 out of 100 games.  This is quite consistent with internet claims that a 40% win rate is possible as I am certainly making mistakes.  Of course 100 is not a very big sample, 37 wins out of 100 is reasonably likely given a true win rate anywhere between 30% and 45% or so.