The program package NaSt2D-2.0 solves with the SOR-method (successive over-relaxation) the Navier-Stokes equations, discreted by finite difference method, in a staggered rectangle grid for given boundary conditions. Viskous, unsteady, incompressible, laminar and turbulent flows you can numerically simulate. The low-Reynold number model and the standard k-ε model are implemented as turbulence models. The program package contains the source files in programming language C, a detailed instruction manual as HTML-file, input samples for all implemented problems, and as FORTRAN-files the preprocessing programs for visualization of computation results with the graphic programs GNUPLOT and DISLIN. It is available free of charge on http://www.nast2d.de.