I had lot of issues on Windows Vista Ultimate (SP1) running PHP 5.2.6 after installing it using the Windows installer. The PHP command interpreter kept crashing.
After mucking around with PHP.ini file and lots of Googling... I finally downloaded the PHP Win32 Zip file from PHP.NET site and unzipped it into the existing PHP Folder and that seemed to have worked for me.
Make sure you run - php.exe at command line. That may give you an insight into if PHP itself is happy or not.
As far as Apache configuration goes, here is what I added in httpd.conf file:
....
LoadModule php5_module "C:/Program Files/PHP/php5apache2_2.dll"
...
#PHP Folder
PHPIniDir "C:/Program Files/PHP/"
# 'Main' server configuration
#
.....
....
AddType application/x-httpd-php .php .html
AddType application/x-httpd-php-source .phps
...
It seemed to work for me. Good luck with your installation. Happy PHPing!
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