If I had two xampp servers on my computer one in the normal C: drive and one on an external Drive. How would I be able to redirect any traffic to the External drive and not the C: Drive. ?

You can set up the servers to run on differnt ports. For example, server 1 on C: drive on port 80 and server 2 on external drive on port 8003. You can then set up port forwarding in your router so that traffic coming to port 80 is forwarded to server 1 and traffic coming to port 8003 is forwarded to server 2.