Other than that, some pieces of old hardware can only run in a physical 2000 or XP machine whether because they can't be physically put in a newer machine due to the lack of interfaces (ISA, ATA, AGP, PCI, etc.) or because its drivers can only run in a 16 or 32-bit operating system.
Yep I have a couple of film scanners that run off Adaptec SCSI PCI interfaces that never got Vista/Win7 driver updates. Quite a few film photographers and labs using XP machines (and ancient Firewire Macs) to keep their Flextights etc alive.
Ethics is relative. I'm sure it is against their ToS and part of the licensing agreement to not reverse engineer and/or bypass activation systems. If M$FT really wanted to they could go after those people, if they could find them. So while I'm sure most of the general public would say "yeah that's fine, M$FT no longer supports the OS nor makes any money off it", lawyer speak and technicalities probably says its still "unethical". But laws and ethics are not the same thing... sometimes they overlap or merge, but they are completely different. Something can be perfectly legal but unethical, and something ethical may be illegal.