File / Folder Tally Tool
I'm sure someone else can provide a more comprehensive answer than I could, Just a few things:


string::at throws an out-of-range exception, since you're not actually catching anywhere, I'd use [] since at() is slower and you're already checking the string length, not that it really matters that much for this simple code though.
I would factor out the std::wstring(argv[1]) and similar into local variables so there are fewer brackets.
if statements without braces are less maintainable. 
wmain is windows specific, so this code won't compile elsewhere.