Changing site url

Hello There,

I have finished installing and working on a wordpress site for one of my clients. currently the site adress is (http://www.abbaqatar.com/Abba_WP). Now i need to change the url to (http://www.abbaqatar.com).

For that I copied the index.php and .htaccess into the directory above(/public_html/abbaqatar).

After that edited the header file url in the index.php file to (./abbaqatar/Abba_WP/the rest)
But when I go to http://www.abbaqatar.com it still shows a blank page.

There were already a site preset. Not wordpress though. I renamed those index files to index_old.html. So that shouldnt interfere with the index.php file. Is there anything else that Im doing wrong here? Please advice. Thanks.

Regards
JAcob