On PC, go to start/run/ type cmd/on the black box type ipconfig /all
Jot down the ip address.
Make sure Zone Alarm (if you have it) is shot down for the time being.
Hover the mouse to the bottom right hand corner over the TightVNC icon and verify that it is the same ip address.
Right click on the VNC icon and select properties/change the password/under the display tab choose full desktop
On the N800, type the ip address/password