Have you created a phpinfo page to verify the settings of the server? If not create a new php page that has just this line of code in it:
php:
<?php phpinfo(); ?>
Make sure to save this page to the sub directory you will be working with and visit the page to verify the results.
Once you do this you should be able to view the installation pages for PowerStore by trying to navigate to the admin area. You should not have any problems doing this with IIS. I have PowerStore 3 running locally on IIS myself.
