also i think this tutorial is good, but it misses some things like you need to have msys-zlib-bin and msys-gcc compiler to able to make libpng and libqrencode.

1.1 Install msys shell:
http://sourceforge.net/projects/mingw/files/Installer/mingw-get-setup.exe/download
From MinGW installation manager -> All packages -> MSYS
mark the following for installation:

msys-base-bin
msys-autoconf-bin
msys-automake-bin
msys-libtool-bin

then click on Installation -> Apply changes

Make sure no mingw packages are checked for installation or present from a previous install. Only the above msys packages should be installed. Also make sure that msys-gcc and msys-w32api packages are not installed.

1.2 Install MinGW-builds project toolchain:
Download http://sourceforge.net/projects/mingw-w64/files/Toolchains%20targetting%20Win32/Personal%20Builds/mingw-builds/4.9.1/threads-posix/dwarf/i686-4.9.1-release-posix-dwarf-rt_v3-rev1.7z/download
and unpack it to C:\