From what I can tell from the fax templates (Word 2000),
the check box is a square character rather than a
functional check box. I have found that if I add a check
box from the control toolbox it gets a tick mark, and if I
add one from the Forms toolbar it gets an "X". The one
from the control toolbox can be difficult to align with
other text. I can't even imagine why there are two
mutually exclusive options for inserting a checkbox, but
there it is. It is possible to format the one from the
control toolbox so that it is almost exactly the size of
the box (no label), but it is a nuisance. Perhaps later
versions of Word have addressed this. If not, they should.