when you run the program 'vncserver' from putty, it will ask you the default screen number you want to use when you vnc into that machine, ex. :1 ,and then you set the login password.
then when you use tightvnc (or similar) to open your x-window, put that :1 on the end of your ip address, ex: 192.168.2.5:1
It it also a good idea to kill the vncserver when you are done with it, as a security measure...
ps -aux (then find the pid number of the vnc process)
kill XXX (the pid number)
have an adult beveridge!