This blog post describes how to set up a basic Haskell development environment on Windows. This is the setup I use to make sure that the network package continues to work on Windows.
The Haskell Platform has everything you need to get started, but it doesn't allow you to build certain packages that require Unix tools, like autotools. For that, you need MSYS (or Cygwin, but the former works better.)
Install the latest Haskell Platform. Use the default settings.
Download version 1.0.11 of MSYS. You'll need the following files:
The files are all hosted on haskell.org as they're quite hard to find in the official MinGW/MSYS repo.
Run MSYS-1.0.11.exe followed by msysDTK-1.0.1.exe. The former asks you if you want to run a normalization step. You can skip that.
Unpack msysCORE-1.0.11-bin.tar.gz into
C:\msys\1.0. Note that you can't do that using an MSYS shell, because you can't overwrite the files in use, so make a copy of
C:\msys\1.0, unpack it there, and then rename the copy back to
C:\Program Files\Haskell Platform\VERSION\mingw\binto your
PATH. This is neccesary if you ever want to build packages that use a configure script, like network, as configure scripts need access to a C compiler.
You now have a basic Haskell development setup and you should be able to install more packages using the
cabal command line tool.