they even have their own key on the keyboard!!
Ah... so that's what it's for... I begin to see the point about users not knowing how to open a new window...

Nah, just kidding. Then again, I was talking to a good friend of mine about a certain site about our shared hobby, and the discussion went something like this:

He: what's with the site lately? I can't see all the way down, and I miss the link to the forum! It's not even taking up the whole screen!

Me: Oh? What browser do you use? Internet Explorer?

He: *sheepish look*

Me: Is there a light blue "e" in there somewhere?

He: *recognition* Yep!

Me: Ah, Internet Explorer. Isn't the window maximized, then?

He: *sheepish look*

Another friend: Does it look like this? *shows non-maximized window with IE*

He: Right! that's it! Why does it do that?!!

We: Oh well, couldn't tell, it does that sometimes; simply hit the button left of the "X" and you're safe.

He: Oh, alright.

So, maybe not all users get it straight away, but he, too, will learn. Eventually.