Makes sense, doesn't it? 99% of nagios is found in the tree under your nagios directory, /usr/local/nagios by default. The other 1% is where your startup scripts are, as jakkedup said.
I am, of course, assuming you installed from source, and not from the included files that are scattered about many directories in a number of Linux platforms.
Edited Thu Jan 05 2006, 10:31PM ]