Windows Applications
If your going to write an application for Microsoft Windows, there is no better choice than .NET

.NET provides a set of classes and API's that make it simple to create robust Windows applications with ease.  Visual Studio, the .NET development environment, is arguably the best Integrate Development Environment(IDE) out there.  Visual Studio has been around for a long time and has come a long way.

One of the largest strengths of .NET is that it is fairly language independent.  You can write .NET applications in a multitude of languages.  While C# and Visual Basic are the primary .NET languages, you can also use implementations of C++, PERL, A++, ADA, J#, and others that I can't think of at the moment.