If your remote machines run Windows 9x, Windows Me or Windows XP Home, you will have to go round each machine to do the job, or else you can incorporate your changes via the network connection script (except on XP Home).
If your machines run Windows NT, Windows 2000, Windows 2003, Windows XP Pro or higher, you can do the job by simply right-clicking on the machine in question then selecting Take control remotely / Reload the configuration. The effect of this will be to update the different parameters stored in the remote machine registries.
Lastly, for the machine to actually take this update into account, you'll need to stop and restart the VNC Server service on the remote machine. You can use our tool to do this.
Note: If you have configured TightVNC so that the service stops automatically (and is thus implicitly started up) every time you take control remotely, you don't have to start and stop the service manually.