Please help. I'm sure this is something really simple but I am new to Zencart and am still trying to get my head around everything

I have my zencart installed at /public_html/jewel
lery_gifts

I have a subdomain (coinwatch.tripleflow.com) pointing to my zen cart installation

I have 2 different templates setup at the moment using the config files:
1. www.tripleflow.com_config.php
2. coinwatch.tripleflow.com_config.php

My problem is in coinwatch.tripleflow.com_config.php
If I set
define('HTTP_SERVER', 'http://www.tripleflow.com/');
it shows properly until I click on a link then it reverts to www.tripleflow.com/product....
but If I change this to
define('HTTP_SERVER', 'http://coinwatch.tripleflow.com/');
I lose the template and images etc..

What am I missing?
Do I have to install my zencart in the Public_html root?

help appreciated
thanks in advance