[dragonwriter]

> The correct form of possessive context for words ending in "s," is with a dangling, trailing apostrophe, and omission of the extra "s."

That is correct (or, at least, nearly universally agreed to) for possessives of plural nouns ending in “s”, style guides are mixed when it comes to other nouns ending in “s”, though the most common rule seems to be to use “’s”; while “windows” is plural, “Windows” as the name of the operating system is a proper noun that is not treated as plural.