I keep my old XP box laying around for the occasional flash to the past that won't run on my (yuck) 10 (64 bit) machine -
Wolfenstein 3D.
I know it is terribly violent, but I didn't play it until I was an adult, and my brain was fully formed - more or less.
But I built it to "last", with a 500gb hard drive, 2gb of memory (two more empty slots) and a dual-core processor (NBD these days).
I'm just telling my story. You have gotten good advice already. Find a good program for wiping the hard drives. I don't know how good reformatting does. If T.V. dramas are any indicator, pesky hackers can get through almost anything, short of removing the platters and running them through a shredder.