What is the exact error message you receive when trying to install these extensions?
It is difficult to have an idea of what the probe may be without knowing the errors massage. Please post back with the exact error text.
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.