Do not let horizontal split be removed

[Cecil Westerhof]

Because I have quite a wide screen I have split my frame in two windows
with 'C-X 3'. In the left window I have the group buffer and the right
window something else. When I open a folder in the group buffer the
right window disappears and there is only one window left with the
opened folder. Is there a way to circumvent it? So the folder is opened
in the left window and the right window stays and does not change?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof