Instant messaging is cool, but wouldn't it be neat to extend the client's capability? You can make Windows Live Messenger do a lot of interesting things by writing a simple .NET class library using C# or Visual Basic: Beginning with version 8 of Windows Live Messenger, Microsoft has allowed users to write code, using the .NET Framework, to interact with Messenger client. By using the Messenger SDK, you can write an assembly that is loaded into Messenger and which will react to events in the messenger user interface. Luckily for us, Microsoft has taken security very seriously in supporting add-ins to prevent malicious use. By default, add-in support is not even turned on in Messenger.

To enable it, you need to add a new registry key. The root of the key is in HKEY_CURRENT_USER\Software\Microsoft\MSNMessenger. Add a new DWORD key called AddInFeatureEnabled and set it to the value of 1. Once you do that, you can fire up your version of Messenger. If you look at your preferences, you should now be able to see a new Add-Ins tab.....