wp-config.php' already exists

Hi
I get this message when using the WP login page.
“The file ‘wp-config.php’ already exists. If you need to reset any of the configuration items in this file, please delete it first. You may try installing now.”

When I click on the ‘installing now’ link, I get this message “You appear to have already installed WordPress. To reinstall please clear your old database tables first.
Log In”

When I click on the ‘Log in’ button I get returned to the original login page. I’m going round in cirlces!

I am however able to access the WP editing pages (Posts, Highlights, Media, etc, etc listed down the left hand side of the page) and edit my site as usual, but I get the same error message when I click on the dashboard link.

What I’ve done to resolve this:
Read through the Support forums and contacted my host provider who has tried several things like replacing the WP-admin files, but nothing has worked.

Please help me resolve my login peril.
Thank you