I have installed Apache both in
/etc/apache2 as in
How can I tell mac to use the
/etc/apache and not the other one?
First, make it so the macports apache install does not run automatically (I'm assuming macports because of the location):
(I'm also assuming you installed apache2.)
Now the macports apache will only run when asked. If you never plan to use that copy of apache, consider
and it will be gone forever (you might have to uninstall things that depend on apache as well).
Use the Sharing panel in System Preferences to turn on the preinstalled apache, or use the apachectl script as indicated by Indrek; e.g., apachectl start
In your case you need to specify an alternate configuration file with :