I've got a perfectly functional tower that I could give to you for cost of shipping. It's a bit of a frankenbox, cobbled together from this and that, and didn't cost me more than $15 or so to make. Currently Windows 98, but I could wipe it and throw on 2k before I sent it off, if you'd prefer that. (Assuming it's got enough RAM, I honestly don't remember. (Also, you'd need to provide your own monitor, keyboard, mouse, etc. But I assume you have those, from the otherwise non-functional computers.))

Also, you might consider Modest Needs for some of the rest of it. Worth a shot, anyways.