I've got one 8086 with a 80 MB harddive running
MSDOS 3.31, stacked somewhere upstairs. My firewall is a P 90 with 3 2GB harddrives, a 4x
cdrom player, 2 ISA 100 Mbit NIC's (those are a bit hard to find), 128 MB EDO Ram (which
was a pain in the ass to get it configured right) running debian with kernel 2.6.1,
firewalling using iptables.
And if that's not old enough, I still have a C64 with
tape drive and joystick stacked somewhere, and the last time i checked it's still in
operating order.