Strange results with trying to start PHP (on Windows). As if configuration is not getting in?
If you manually install PHP as a Apache HTTPD module, you have to know, that you manually have to copy the php.ini file to its default location. This behavior is in PHP installer version 5.3, but it may stay forever.
Is this my problem?
You could check it with in phpinfo(). Look for "Loaded Configuration File". If it has value "(empty)", this is your case.
The default path for the config file is c:\Windows (if we have to be more correct, it is %SystemRoot%), so copy php.ini there and start correcting it. That's it. Solved!
php.ini could have per-user location, but for that you may check in google.
P.S. The first symptom of the primary evil was not loading of php_mysql.dll with the line "extension=php_mysql.dll". The error message in OS Commerce was "mysql The MySQL extension is required but is not installed. Please enable it to continue installation."