Saving window config using desktop globals

[Tim Johnson]

Using GNU emacs 24.3 on ubuntu 14.04.

I use the following method
(add-to-list 'desktop-globals-to-save 'current-project-directory)
(add-to-list 'desktop-globals-to-save 'kill-ring)
to save certain variables.

How may I extend this method to save and retrieve my window
configuration? 

at this point, I'm not using more than the default
frame.

I'd like to do this without installing another package. I'm thinking
about using a dedicated register to save one or more configs.

I've tried using C-x r w <ENTER> to save it. But when I restart
emacs and try C-x r j, I get the following:

jump-to-register: Register doesn't contain a buffer position or
configuration

TIA
-- 
Tim 
http://www.akwebsoft.com, http://www.tj49.com