While attempting to run nginx from a command prompt the following error was presented:

nginx: [emerg] bind() to 0.0.0:80 failed (10013: An attempt was made to access a socket in a way forbidden by its access permissions)

To see what local process was already listening on port 80 I used TCPView v3.05 from SysInternals.  Turns out it was Skype.  After quitting Skype, nginx ran successfully.