If you are trying to access your RH box from Windows, you need to have vncserver running on the RH box and a vnc client running on the windows box. When you start vncserver, you will see it start on a particular window, usually :1 if there are no other instances of vncserver running. So from your windows box, point your vnc client to the ip address and window of the vncserver.
So lets say your RH computer is at ip address 192.168.1.100 and vncserver is running on :1. You would try to connect to 192.168.1.100:1, NOT 192.168.1.100:5901