I once went to some effort to recondition and setup a used PC for a family that didn't have one. Even as I set it up, I knew this was dumb. They couldn't afford a network connection, they didn't have a printer and couldn't afford a new one, and they didn't have the background or resources to maintain the high quality computer I gave them. Since they couldn't affort to pay to dispose of it, I was just creating more toxic waste. (I'd said I'd come get it ... but that was dumb too.)
As in the twin cities, so to in Africa. Even if all those donated PCs were in terrific shape, most of them would soon be worthless. PCs are annoying resource intensive life sucking leaches that cost far too much to maintain and keep healthy. And here I'm speaking of a Mac. Wintel macchines are far worse.
Stop donating computer hardware. It's a waste. Spend the time and effort lobbying for decreased tariffs and support increased trade. Support acts that can decrease poverty. Donate to CARE.ORG. Donate high quality t-shirts. Just don't send computer gear.