failing to connect to server

[David Bull]

I am an amateur user.  I have used VNC very successfully to connect to 
my mother's Windows XP machine from my own W2000 PC (over a dial-up 
connection) in order to help her out with problems.  I am now trying to 
do the same for my father-in-law, but am not succeeding and don't know 
why.  He has opened WinVNC server on his machine, and has told me the IP 
address he gets when he hovers over the icon.  I have entered this IP 
address in the "new connection" window of the listener on my PC.  I am 
then getting a "VNC Info" message which says "failed to connect to server".

The only possibilities I can think of are:

- the connection is being blocked by the Windows XP firewall in my 
father-in-law's computer?  Is this possible?  Should he disable it?
-  does he need to "add new client" on his machine (I didn't think that 
was necessary?) - if so what to put in the box?
- would it be a problem if we were using different versions of VNC? Mine 
is 3.3.3 R9.  His may be an earlier one (it came with his machine).

What else could be going wrong?

I have read all the FAQs etc, but can't see what I could be doing wrong.

Hope someone can advise me.

regards

David Bull