I have no idea what that error is. Take a look at http://www.adobe.com/devnet/dreamweaver/articles/setting_up_php_05.html, which describes how to define a testing server for PHP. It uses XAMPP, but the basic principles are the same.
I got this error as well. My issue was that I needed to have the website setup with the same directory for storing files as the directory to which you point the root of your site.
For my site: www.mysite.com (don't go there I made this up for the example)
Where on your computer do you want to store your files?
And next it asks:
What URL would you use to browse to the root of your site?
The latter should be configured according to the link that was posted earlier by David Powers.
When I had these two mismatched (trying to store the files elsewhere), I got the HTTP 12150 Error. I don't know if this is the exclusive solution to this problem but it fixed it for me. I'm still getting a warning about a prefix causing potential link failures but I can't really figure out what's causing that. Seems to be more of a warning.
i had the same problem on which i found a simple solution for.
i have a local testing server and a remote server (both are ASP.NET C#)
i define the site as follows :
HTTP URL address : http://www.bunnyslots.com
Server Technology : ASP.NET C#
Edit and Test Localy : D:\Websites\bunnyslots.com\Site\
Testing Server : http://bunnyslots.loc/ (this url was made up with the hosts file change, i added "127.0.0.1 bunnyslots.loc" to the hosts file),
this is where the problem appeared and solved, when i havent entered the last / on the end of the address, i got the same error 12150,
when i added the last / to the address, everything works fine.
i hope this helps anyone...