VB6 has nothing to do with .NET.
However, you can always start any application via Shell, see http://www.msfn.org/board/topic/35615-vb6-lauching-a-program-or-file-with-params/
Let me tell you: chances are, you are going in wrong direction in principle.
This is little good in running other applications from yours; and VB6 is dead, a curse of many software developers who got VB project as legacy. Why? All VB.NET and C# compilers come free of charge with .NET Framework (surprise?) and even Visual Studio Express is free of charge. You can also use Open Source SharpDevelop, http://en.wikipedia.org/wiki/SharpDevelop
] — any of the above is much better than using VB6. You could use some VB6 only in desperate need to support some VB6 legacy, but when you're already dealing with .NET, all that comes to a complete absurd, just don't go this way.