The Windows Component Store (aka Side-by-Side aka WinSxS) is sort of a content-addressed store for DLLs and the like, except the content-addressing isn't facilitated by a literal cryptographic hash over the contents, but instead by the logical identity of the component (name+version but more). And, it doesn't fetch anything automatically. Writes to certain paths are just intercepted and redirected into it, while storing an association somewhere else that the app that did that (or was installed doing that) wants that particular component (or at least, that's how I think that works).