I have 5 old PCs sitting in my storage right now. Probably 3 of them would boot up if you plugged them in today. One of them is basically unused because I was getting a RAM error when booting it up and could never clear it. I finally gave up and just purchased one already built.
I had several full computers too until COVID. One of my projects during that time was organizing old pics etc. I bought one of these and just too the hard drives out of them. Works a charm