Andrew et al.
Further to my last message, the extra options I mentioned appear to be those that work with a normal X server (normal, rather than nested).
One interesting use for this is to open a session on another unix station that uses XDMCP to log in and where you wouldn't want the session and window managers from that other machine interfering with your local machine. Just say:
Xnest :1 -query hostname
Where 'hostname' is the host you want to log in to. The other options are documented in the man page 'Xserver'.
Steve.