Following are steps by steps (with screen shots) on installing PHP on Windows 7
(1) Download from PHP site
http://windows.php.net/download/
For this time, best if you download the zip file (Thread Safe) instead of the .exe installer. It was said that there are some known issues with the .exe installation as some of the libraries or files needed for MySQL are missing
(2) unzip to a directory, in my case, I extract it to C:\php
(3) Rename the following file:
C:\php\php.ini-development to C:\php\php.ini
==> 
(4) Manually create C:\public_html
(5) Configure doc_root at php.ini
Find “doc_root” and configure it your Apache DocumentRoot.
*Click here if to find out where is your Apache DocumentRoot ??
==> 
(5) Configure extension_dir at php.ini
Find “extension_dir” . Uncomment the Windows part, and point the “extension_dir” to <Your PHP Directory>\ext
==> 
(6) Configure Apache Conf file
LoadModule php5_module "C:/php/php5apache2_2.dll" AddType application/x-httpd-php .php PHPIniDir "C:/php"
(7) Restart Apache Web Server
(8) Create test page
<?php phpinfo(); ?>
