I am fluent in C, C++ and Intel Assembler (X86 and X64), and have worked on many applications over the years. Most of my experience has been on Windows platforms, using COM, MFC and Windows Forms.
To a much lesser extent, I have worked in C# with the .NET Framework and WPF. If you go back in history, I have also written applications in BASIC, FORTRAN and IBM PL/S.
I have written device drivers for Windows on several occasions.
If I have a specialty, it is in debugging and performance optimization.