Windows XP is 5.1.2600. That extra zero is incorrect, no matter what spin you try to put on it. Hidden zeros or whatever, what is the problem with making it say 5.1.2600? Goto Start > Run > winver. See exactly what Microsoft think
Version numbers are
not based on maths.
01 is not the same as
1. Why there are extra zeros is a question only Patchou can answer. It's true its only a tiny bug, but its easy enough to fix it to accurately display the correct version number.