Another possible reason is access control. If you start a process on system A and this process wants to display a window on the display of system B then system B has to allow this access for system A first.

On a UNIX system this is usually done with the xhost command, the most common form being:

Code:

xhost +

which simply disables access control (allows every host to display windows).

It might be that XP lacked (had deconfigured) such an access control whereas Windows 7 has this enabled.

I hope this helps.

bakunin