When installing OsCommerce for the first time you may receive this error:
Server Requirement Error: register_globals is disabled in your PHP configuration. This can be enabled in your php.ini configuration file or in the .htaccess file in your catalog directory.
To enable register_globals for your account, you will need to edit the .htaccess file in your OsCommerce root directory. There should already be an .htaccess in there, and you should just have to comment out these lines (may vary per version)
If you are on a PHP 5 server, you should change mod_php4.c to mod_php5.c. If you do not have an .htaccess in your OsCommerce directory, you can simply create one and insert the above lines.