Preserving window layout

[Matthew Calhoun]

Hello,

I'm trying to set up Emacs in a way that I think will be nice for 
coding: I have a single full-screen frame with two large side-by-side 
windows for editing source files and whatnot, and below these two 
there's a third window with a shell in it, which takes up the entire 
frame width. It looks something like this:

-----------------------
|          |          |
|          |          |
|  source  |  source  |
|          |          |
|          |          |
-----------------------
|        shell        |
-----------------------

Sort of a poor man's IDE. The problem is, when I do something like 
command-apropos it wreaks havoc on my nice little environment - the 
shell buffer grows to take up half of the frame, and the *Apropos* 
buffer has taken the place of *shell*.

What I would like do is keep this basic layout the same, viewing 
various buffers only in the top two windows, and keeping the shell 
window undisturbed at the bottom. So, is there some way to "lock" a 
screen layout, or at least a single window? And can I prevent my shell 
buffer from being replaced by other buffers?

In case it matters, I'm using Emacs 21.1.1 in Mac OS X's Terminal 
application.

Thanks,
Matt