There is a known problem with the OScommerce power tool that will cause conflicts when running this on a website that does not have an SSL certificate.
Below you will find the solution to fixing this:
(Example: you installed it into /oscommerce )
You will need to FTP into the site
Change to the directory /var/www/html/oscommerce
Now, from here, you have two files to edit:
You will need to find the following in these files and change:
Copyright (c) 2004. Datona Communications. All rights reserved.