What browser are you using to download? Most browsers will have a Save option you can choose to save the file instead of installing it and then you can open the Dreamweaver Extension manager and install it from there.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.