In some cases, VB Migration Partner fails to correctly locate or load the .NET assemblies that aren’t referenced by either the VB6 project being migrated or the converted .NET application. In such cases, you can diagnose and often solve the problem by means of a .NET tool named FUSLOGVW, which clearly displays which .NET assemblies are loaded and which aren’t, and why.

You can learn more about FUSLOGVW by reading this introductory MSDN article.

If the problem occurs on a computer where Visual Studio isn’t installed, you might find the following thread.