This error is triggered because the permissions on the file are set to Read,Write and Execute (UNIX) or on Windows no attributes are checked in the file properties.
On LINUX/UNIX: Open the /includes/ directory and using CHMOD, set the permissions to 444. (Some systems may prefer 644)
On Windows: Open the /includes/ directory, right click on the configure.php file and check the "Read Only" status.
Sometimes you have to do this via a File Manager tool provided by your webhosting provider. In cPanel, ...