Well, if MS Word is installed by unpacking a separate package, then
it's merely data from the installer point of view. In this case, yes,
the installer can be GPL'd. Just as dpkg(8) which is GPL'd, but, of
course, using it to install a non-free deb package is not a dpkg
copyright violation.
It seems to me that the conclusion would be different if MS Word
binary files were hardcoded as strings defined in the installer
source code. In that case I would say the GPL'd installer is a
derivative work of MS Word and thus undistributable. Anyway, I see
that there are some people who claim that hardcoding a work as a
string included in the source code of a program creates
aggregation/anthology rather than a derivative work... So I expect
that those people disagree with me on this latter case...