For all my life, most of my computers have been hand-me-downs or upgrades. I've built a handful of PCs from scratch, but even most of the ones I built with new processors and motherboards had some hand-me-down parts. But it seems like recently a threshold was crossed where the computers available to just anyone (and not someone who knows "someone") for basically nothing began to be pretty good.
My very first computer was a used C= 16, but I never owned any storage devices (not even a tape drive) so it hardly seems to count. But shortly after I got my first new computer, an Amiga 500. That got me on the road to the wider world of connected computers, starting with BBSes and then AmigaUUCP. When it eventually died, I was lucky enough to get a hand-me-down IBM PC-1 for free — yes, the original IBM PC, the kind with 64kB of RAM on-board. This one had an AST expansion board intended to fill out IBM XT machines with another 384kB, which put me up to 448kB. That was enough to run quite a lot of your basic IBM software, including Telix and UUPC.
After the Amiga, though, the PC seemed like a jail. It had no graphics and only the most rudimentary noisemaking ability, and was woefully slow. It was difficult to run anything on it, let alone run anything at a good clip. Only text-based games would work on it at all. A hand-me-down computer was still a pathetic thing, and of very little use to anyone.
The kind of computers I'm getting now for basically nothing, on the other hand, have finally crossed over into worthiness. I regularly visit a large thrift outlet in my area, which is a fun little addition to a common day trip down towards the Bay Area. While I've long been seeing Pentium 4 machines there, the Core 2 Duos have finally begun to appear. On my last trip I got an HP 4600T-based system with a lightscribe DVD-ROM.
Around five or six years ago, I picked up a complete Athlon 64 X2 4000+ system for $125 with a 20" LCD, because the users couldn't figure out how to get in to the recovery partition any more and had simply bought a replacement system. That's not really that exciting, but what is interesting is what's happening to this class of machine on eBay. You can get enough CPU, RAM, cooler, and motherboard to build yourself a SFF media PC for under a hundred dollars. I know, because I've just done it for $50, less storage or a case. I'm building a case for a CarPC out of a jewelry box. More on that later.
I've written before about how old, slow computers are now pretty fast. But now, old slow computers are not only pretty fast, but they are available for basically nothing. I paid less than five bucks for my latest C2D.