redirect xwindow

[brouwers roland lx]

The following situation:
I am using VNC and on the desktop I start Putty to connect to my
application. In the application, p.e. creation of contracts for leased
cars, I do a system call which brings me down to a Linux shell, where I
can execute the command 'display' (system "display carpicture.jpg"). As
you already understand, I want to display the picture of the car. 

After the execution of 'display carpicture.jpg, I get the error:
display: unable to open X server

So when I enter the following:
$ export DISPLAY=localhost:0.0
$ xhost +1
still nothing happens.

When I open een Terminal window as user Roland, the picture is
displayed, without the commands above.

Is there anybody who understands this.

One should be clear, I am using VNC not MSwindows. I have the same
problem with Ltsp.

I browsed the web for some howto's on this, but I still do not
understand.

C.A.T. bvba
Antwerp-Belgium
roland at cat.be