That's true, if the hardware or OS limit you then there's nothing you can do about it, that's a given. If you install more RAM than the hardware or OS can access, it will NEVER be used. However, even if the hardware and software support more, if you typically never need more than 8G but you install 16 or even 32G, is it worth it to you to have spent the extra money for that additional RAM that may only be called into play occasionally?