Just in case anyone cares, the Express Editions of all of Microsoft's Visual Studio products (Visual Basic, Visual C++, Visual C#, etc..) are all free for download for this fiscal year only. So if you hurry over to MSDN and download them, you essentially get the best Windows compilers out there for free. Not a half bad deal.
As for Halo being coded in Visual Basic.... I really, really, really, really doubt it. While it is true that VB is Turing-complete, the general consensus seems to be that its a gimped language. I'd bet my right leg Halo was coded in C++/Assembly.