Installing user-atc package on windows operating system

please *always* copy the mailing lists on your replies. so that other
people see how issues are resolved.

the standard make/build system of LAMMPS requires a unix-like
environment, with a bourne shell and the typical unix shell tools.
thus building windows binaries with a cross compiler is comparatively
easy (the worst part was figuring out how to write the installer
script and debug it).

unless you have a specific need i suggest you install the pre-compiled
installer packages i pointed out.