Hi,
JimDog
So, Can I control remote windows computers by VNC? Forwarding X11 is convenient b/c you don't need to know the IP of yourself (useful when you are behind a router or firewall).

Not 100% sure I understand what you mean about "not knowing the IP of yourself". If you're on Windows you can just to an ipconfig and on Linux you can do ifconfig. Maybe I missed something.

With X11 I was able to launch linux apps running on my linux box, but I'd see them on my Win2k box at work. I was also able to lauch an entire desktop session (gnome) but again, it's very slow.

With VNC on Linux you see your entire desktop by default, but it's slightly different than running VNC on Windows.

On Windows you have one session, when you login with VNC you see that one and only session....in other words, someone sitting at that Windows computer will see your every mouse move. With Linux that's not the case, you can think of the VNC sessions on Linux as a separate login. Does that help or did I totally misunderstand your question?

Hehe, What I mean is whether I can login into windows XP from another computer if I use VNC.

"not knowing the IP of yourself" means that if I use X11 forwarding in ssh by "ssh -X", then I don't need to know my own IP and I can also control remote linux box. Ipconfig is no use when you connects to internet through a router. Am I right? Because the IP is the true IP, and the graphical interface of apps can't be forwarded back to my computer by an artificial IP address, even with the IP of the router(here, I mean the server computer), it doesn't work(I tried that.). Not sure if I cleared up all misunderstandings.

Oh....yeah VNC rocks! VNC has been ported to lots of different OSs....as long as you have a VNC Server running on a machine (be it XP, Linux, 2k, 98, etc etc) then you can connect to it via the VNC client (again, any client OS, XP, Linux, 2K, etc etc).

I think I understand what you're saying about the IP stuff now....true the router will have the "real IP" while you have the internal network/private IP. This does become a problem when going through a router / proxy say at work....in my case I can connect home through my works' router, but I haven't been successful going the other way (from home to work) and I think it's because of exactly what you're saying....I still need to try some more though.