If you have installed simpleContact on your personal computer (e.g. for testing), you may get this message:
"An error occurred when connecting to the database. Please check that you have configured and installed this system correctly."
A likely cause is that "localhost" is not recognised as the address for your MySQL server. If this occurs, open sc_config.php and try setting the $server variable to "127.0.0.1". It should now connect successfully.
This is a well known MySQL issue, not a particular fault of simpleContact.
Please note: You should restore the $server variable to "localhost" (or the specific address of your database server) before uploading it to your website.