I also wanted to move the local host files to an external hard drive.
The issue I had was spaces in the hard drive name or folder name. No matter what I added +Space it would not work. It did however work when I changed the hard drive and folder name removing the space(s) and then mapping it something like:
DocumentRoot "/Volumes/HDD_NAME/WebServer/Folder_Name"
So now Dreamweaver or other edit is mapped to the external hard drive and the http.conf file is mapped to the external hard drive saving 100GB of my small internal hard drive's space. Of course, this means I can only edit and test locally with that external hard drive attached.
I am using the http://localhost/~username/. Is there a way to access it with the IP address. Currently when i access it with IP adress, I get
Forbidden You don't have permission to access /~username/ on this server.