I program VB6 (self-taught) and I'm thinking of doing a programming course...

Which language is the most advantageous at this point in time? (1)

C, C++, C# or VB.NET

If C, what should a student be knowledgeable on and understand before attempting to learn it? (2)

Where can I find a 'Hello World' tutorial for the C languages? (3)

TIA.

Regards, Dodger.