Well, here we go.
Until very recently, I would have told you that I still occasionally use a 1989 self built 486 machine, running DOS. Specifically, because it is far easier to directly import or export bytes of data or machine code via the parallel port in DOS, than on current tech. Alas, it has now bit the dust, and I have cannibalised mobo for anything usable. I now have to use a Raspberry Pi rig, and USB, which is not as convenient.
I also use a clunky laptop: Fujitsu-Siemens Amilo Pro v2030, running XP and a Linux. (actual variety changed from time to time) It was given to me, but I think it is of year 2005 vintage. Not used for my general usage: it is my garden computer, and if I want to listen to my music whilst gardening, it does the job, and is of low value so not concerned that it could be vulnerable to damage when used in this way.
Also, I use a self built desktop, circa 2005 vintage, when I upgraded it to use the latest socket 939 processor. Kept partially for sentimental reasons, as first built a year or two earlier when AMD first released their 64 bit processor.
For this machine, I have my OS on plug-in drives: a range of Linux flavours, but also XP, which has a useful applet not available in later MS OSs: easily can select output so that MIDI files play on my connected MIDI musical instruments. (Also MIDI playing's stop/start and volume controlled from MS media player.)
Even my general use machine: the one from which this message comes, is a self built 2016 machine. An Intel i3 processor on ASUS mobo: A Z87 Pro, and 32 GB RAM. Been good, but is getting a bit long in the tooth now, so thinking of next build. Which is really why I have joined this forum, as I only assemble PCs from time to time, and find it very difficult to stay up to date regarding best choice of components to use.