the address:
index.php
maps to the following location in IIS:
c:\inetpub\wwwroot\index.php
If your powerstore files are stored in a sub directory of the wwwroot folder, you need to adjust the path you are using accordingly.
For example, if the powerstore files where extracted to:
c:\inetpub\wwwroot\PowerStore\
the address to use is:
index.php