Following things you need to check and make it work on paid osCommerce module:
Create backups not backup folder under /httpdocs/admin/backups
Create cache folder under /httpdocs/ and /httpdocs/admin/
Enable register_globals > ON
Select open_basedir from whatever change to {DOCROOT}\ from the drop down menu.
Select session.save_path from whatever change to {DOCROOT}\tmp and no need to create tmp folder on /httpdocs/
Select PHP Support version 5.2.x above
Select PHP run as FASTCGI application
Enable CGI support
Enable Perl Support.
