##Building hmatrix on Windows 7
Replace minghc-7.10.2-x86_64\ghc-7.10.2\mingw
with
mingw
from x86_64-mingw32-gcc-4.6.3-release-c,c++,fortran-sjlj.zip
Here you have a full Fortran compiler, not shipped with minghc-7.10.2.
So you should have the following
$ gcc --version
gcc.exe (niXman's build) 4.6.3