PowerStore is not a dreamweaver extension. It is a web application. you must browse to the PowerStore files in your web browser to begin the installation.
In the directory you install XAMP to, there is a folder called htdocs, for me this is at:
c:\xamp\htdocs
create a folder named PowerStore3 at that location:
c:\xamp\htdocs\PowerStore3
and extract the PowerStore files there.
Then enter the following address in your web browser to start the installation:
PowerStore3