If this is a new installation you should create
C:\php4 and copy the files under
\php4 to this directory. If you have an existing
PHP installation (for example, with Apache) or intend to have one, you
will need to put your php.ini file in here too.
The files that are in this folder by default are PHP or PHP-GTK-related
and will all need to be updated from time to time. Note that
C:\php4 is the default directory and that if you
install PHP-GTK anywhere else, you will need to specify the full path
as your extension_dir in the copy of php.ini that
is being used by PHP.