The error you are getting is not from any of our extensions, it is coming from Dreamweaver. It is telling you that there is a problem with the way that the testing server is setup. The message is saying that the script file cannot be found in the location it is looking for it. This is one of Dreamweavers internal resources that are used to manage your site. The file and location it is looking for is:
Based on your site settings it looks like your testing server URL is wrong, if the web root for xamp is located in C:\xampp\htdocs\ then the URL for the testing server should be like this:
The localhost will map to the root of the web server so you should not list the folders that come before this.