Regardless of what that manual page says, it's actually deprecated to copy DLL files to a SYSTEM folder. Instead, you should read the instructions on this man page: [man]install.windows.manual[/man]. Specifically, you need to copy the DLL files into the main folder PHP is installed in and then add this folder to your system's PATH environment variable (don't forget to restart after you make this change!).
Also... where does phpinfo() say your php.ini file is located? Where is this file actually located?