Multiple instances

Hello,

first of all, I am a beginner in wordpress. So please be patient 🙂
Ok, here is my “problem”:

On my hoster I have 2 wordpress installations. Lets say ./dom1 and ./dom2.
My current domain (lets say “domain1.com” is pointing to the root and redirected to ./dom1.

index.php in root:
define(‘WP_USE_THEMES’, true);
/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . ‘/dom1/wp-blog-header.php’ );

In the second wp instance I build a complete independent site (this will be “domain2.com”).
Currently I am reaching the directory ./dom2 via “domain1.com/dom2”..thats good for testing the site, but not so good, because search-engines are also indexing this new (not public) instance “dom2”.
How can I prevent, that directories below the current wp-instance are reachable?
current root:
[dom1]
[dom2]
[stats]
[error]
index.php
.htaccess
.htpasswd

Thanks!
Best regards
Ernst