php.ini

Copy the file, php.ini-dist to your %WINDOWS% directory on Windows 95/98 or to your %SYSTEMROOT% directory under Windows NT, Windows 2000 or Windows XP and rename it to php.ini. Your %WINDOWS% or %SYSTEMROOT% directory is typically: c:\windows for Windows 95/98, c:\winnt or c:\winnt40 for NT/2000/XP servers.

php4ts.dll

move php4ts.dll to the windows/system (for Windows 9x/Me) or winnt/system32 (for Windows NT/2000/XP) directory.

Modify httpd.conf of Apache Server

   LoadModule php4_module C:/PHP/sapi/php4apache.dll
   AddModule mod_php4.c
   AddType application/x-httpd-php .php
   AddType application/x-httpd-php-source .phps