[wot-Mike]

Well, most settings are done through the control panel now. I'm having troubles finding various things too, but it's just a matter of playing with it, and learning the new layout.

Ok, where to find various options in the SigmaChat control panel:
* Log in here - http://www.sigmachat.com/login.html

* Click on User Accounts, and then on Options
/nick Command -> disabled
Disable Automatic User Registration System for now
Allow Guest Access = Yes (also for now)
Ghost Users - If IP matches
This will kick any previous login by the same username coming from the same IP address. This will unfortunately leave the old window open in the SigmaChat login screen. Choosing "Always Deny" will leave the new window open with the loginscreen. But the "if IP matches" option will at least stop your users from kicking other users by logging in as them (ok, there's still users coming from behind the same proxy server. Let's hope no one of them will discover this funny option....)

* Click on Websites, and then on Settings
Exit URL -> http://whatever you want
or Exit Url -> javascript:window.close();

This will either redirect the user away from the logout screen, or
the last one will try to close the window, but only after prompting the user first (just the first time though)

As for chatbit, this really should do the trick:

<applet codebase="http://client.sigmachat.com/current/" code="Client.class" archive="scclient_en.zip" width=$setwidth height=$setheight>
<param name="room" value="YOUR ROOM NUMBER">
<param name="username" value="$username">
<param name="autologin" value="yes">
</applet>

I've been having some issues with people logging in multpiple times. The above settings will help a bit, but there's enough holes left (Ghost Users). Right now I can think of a few solutions, but the best bet is the new script. That will register users and log them in using their name and password. You can then disable Guest access, which will effectively kill the possibility to login multiple times using multiple names.
Since loginnames and passwords will be stored inside the vB database, installing the new script won't be as simple as the current version.

Hope this helps.