Using UNC path with credentials
It might be useful for you to use the NetUseAdd function from the windows api http://msdn.microsoft.com/en-us/library/windows/desktop/aa370645(v=vs.85).aspx. It allows you to access a directory through its UNC path.
Looks like Win32 APIs are the most common way to handle this. Check out this SO postAccessing a Shared File (UNC) From a Remote, Non-Trusted Domain With Credentials