If you are doing a lot of Scientific Computing and you want to use Windows as a platform, then my advice is to switch on Linux/Unix. If you don't agree with me then a good solution for you is Python(x,y).
What is it? From their web site:
"Python(x,y) is a free scientific and engineering development software for numerical computations, data analysis and data visualization based on Python programming language, Qt graphical user interfaces (and development framework) and Eclipse integrated development environment."
"Its purpose is to help scientific programmers used to interpreted languages (such as MATLAB or IDL) or compiled languages (C/C++ or Fortran) to switch to Python. C/C++ or Fortran programmers should appreciate to reuse their code "as is" by wrapping it so it can be called directly from Python scripts."
For the complete list of features and its components checkthis page.
For some screenshots check here.