retrocomputing

I've got a couple of older Dell core2 machines with ddr2. They still have good caps in them. They're interesting to me because they have 3.5" floppy and sata cd/DVD and they can handle a newer os. Id like to keep something around that I can pop in an old cd/DVD or floppy disk or create disks from. I'm just stuck on if I should install xp, 7, 10, tiny 10, some flavor of Linux, they have vista stickers on them. They're just in a weird spot where they're not really vintage PC's and not really modern anymore either.