How can I launch X window?

[Esteban Benítez Cambreleng <ebenitez@xxxxxxxxxxxxxxxx>]

ˇHello!

It´s the first time that I use Ferret. I´ve windows XP.
When I've finished to setting up it, and i run the example (go ptest) 
the screen shows this message:

"Can't connect to X Server :0.0
 Your DISPLAY environment variable must be set to
 point to a working X server." 


I've tried to change Display´s value but it ever appear 
the same message. it only varies :0.0 which depends the given value.


                                        Thanks for yoour Cooperation

                                           Esteban (SPAIN)

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