X Window Server/Client Software

Hi,
I am planning to setup an X window server/client for my Linux ES 3.0 box. Is there any recommended software that we can use (the client is MS Windows XP). We prefer to have Xterm running on top of SSH for security purpose. VNC is good, but can’t differentiate between Linux users, also not secure (by default).
The solution can be free or paid software.
Any idea is greatly appreciated.
Thanks