In reply to Blue Straggler:
>which puts them to a second use in rural sub-Saharan Africa to improve education.
There used to be a lot of this, but it was abused as a way to dump crap kit in the third world. People don't want old, slow machines, that don't run a modern OS and eat power. What tended to happen was that kit sent to the third world, with the best intentions, was scrapped, in an environmentally horrible way. Circuit boards have more copper per ton, that copper ore.
As for your problem, I'd stick linux on them, if they'll run it. Putting them on freecycle / freegle, is probably the best you can do.