In this paper we will give a short introduction to the installation and efficiency of state-of-the-art direct solver packages like CROUT and UMFPACK for linear systems, combined with highly processor optimised BLAS libraries. We will give an overview about the methods that can be used to integrate these libraries into Fortran programs compiled with the Compaq Visual Fortran or the Intel Fortran Compiler using Microsoft Windows. In numerical examples arising from the numerical simulation software SILO we will show that these packages provide a very effective way of solving medium-size (about 30.000 unknowns) ill-conditioned problems as long as a highly optimised BLAS library performs the low level linear algebra operations.