Why does have to be in MS Word? Why don't you generate the desired diagram and then insert it in the document? Paint should be able to generate those for you, I'm pretty sure. Well, I can't remember if it had arrows, if not, that might be a bit annoying, but other than that it does exactly what you need. Alternatively, I'm sure there are a bunch of free tools for various types of charts generation, including flowcharts.
I've used Dia and Visual Paradigm before - both, admittedly, for UML but I'd be surprised if they can't do flowcharts or even what you need. They both can be used for free[footnote]the former completely, the latter had a trial version which was perfectly usable for the period, which was about a month[/footnote] and worked fairly well. Other diagram software I remember I've used are these
- BOUML - I think it was advertised as simple and functional, and I think it sort of was, but I also remember I didched it for some reason. I think something was really, really annoying to do or some simple, yet needed, function was just impossible. Maybe it works better now or it might help you, I dunno - you can give it a try.
- Umbrello - I'm pretty sure it's on Linux only. Specifically, it's a KDE tool, in fact. I did use it in Gnome (it dragged in A LOT of dependancies) and it worked fairly well, aside from a few bugs but I'm fairly sure those were because it wasn't running on KDE. But overall it was really easy to use.