So what do folks here do with their old PC when it comes time to upgrade to a new machine. PC World has a good article, They even suggest turning it into a fish tank What to do with your old PC - PC Gamer
I've done most of those things with my old computers but have never turned one into a fish tank.
I usually try to hand an old PC down to a family member but I have also advertised fully functioning computers on Craigslist as free to whomever. I gave 4 away last year like that.