I agree with the idea that there should be a tooltip to show what the
greyed out section is for, although to me it is usually pretty obvious
what it is connected to, some users might not find it that easily.
I also agree that making them invisible is not going to be helpful at all.
However I thought that at least in some programs that there is an
option that can tell you what greyed out sections are, the ? in the
upper right corner of the window. Most times if you click that,
and then click in the window somewhere, you'll get an
explaination. Not all programs use that, but it is there.