Trying to use mod_rewrite on an Apache server with no luck.

Apparantly it is installed by default; I just need to turn it on and
define some rules. The problem is I can't find any mention of
mod_rewrite in the httpd.conf file.

I've tried adding the following line to the httpd.conf file:

    LoadModule rewrite_module modules/mod_rewrite.so

Restart Apache and all I get is page not founds until I remove that
line again.

I've noticed mod_rewrite.so does not exist in the modules directory.
Should it be there?

SUMMARY: How do I enable mod_rewrite under Apache and test if it is
working?

perhaps this will help:
http://www.sitepoint.com/article/910

What OS are you using?

Yes, mod_rewrite.so should be in there.

The only way to test it is to create a rewrite rule in the conf file,
in the doc root:
<Directory "/var/www/html">
Options FollowSymLinks
Allow from all
RewriteEngine   on
RewriteBase    /
RewriteRule     ^old.html /new.html [R=permanent]

</Directory>