Its petty easy. I use C# to make my MapPoint 2002 and 2004 COM add-ins. Just compile with the IDispatch interface (or use the Office XP/2003 SDK for Visual Studio.NET) and tell it to create an Add-in only for MapPoint. Then add your refrences, remove all office traces from your files and compile and run the setup program it provides at least once after you build (to setup the links to MapPoint for your dll) and your set.

Happy Coding.