I have to develop an application for windows that will enable controlling the mouse through web cam by recognizing hand gestures. I will be using vc++ 2008 for development. But
Unless you are a very experienced C++, programmer, C# is a much more productive language (speaking as someone with over 15 years C++ experience and 2 years C#).
The .Net libraries offer a wealth of high-quality functionality that's easier to use than the standard C++ library.
So, I'd go with using .Net.
I also recommend using C++/CLI to directly call complex native libraries if you have to integrate them, rather than P/Invoke. That's good for odd calls but doesn't let you easily access data structures or mingle native and managed code.