For putty settings, in the left pane choose Tunnels under
Connection and SSH. Choose Enable X11 forwarding.
Save this as a default setting.
Then, when you ssh into something like tango.cs.odu.edu, X
should be forwarded automatically, and you'll be able to open xterm
windows (and emacs and xgraph and nam, etc). To check this, type:
printenv DISPLAY
You should get something like tango.cs.odu.edu:10.0, for
example if you're on tango.
If these steps fail, you can typically set the display manually.
Find the IP address of the Windows computer you're using, and at the
Unix prompt type:
setenv DISPLAY ip-address:0