In the comments of a recent post I did, reader Glaurung Quena brought up a good topic: secondhand PCs, acquired cheaply, strictly as rebuild fodder.
I like the idea, of course, because I’ve been doing it for years. In the 1990s I built a lot of 486s and Pentiums into former IBM PC/ATs, basically until all the board makers relocated the memory slots into a position that wasn’t clear on the original PC/AT due to a beam that supported its drive bays. And of course the adoption of ATX and MicroATX killed that, at least for a while.
But now ATX has been around as long as the old AT architecture had been when ATX came along, and efforts to replace ATX haven’t been successful. So that trick makes more sense again. Buy a secondhand machine cheaply, intending to re-use the case, and regard anything else inside that happens to be reusable strictly as a bonus.