True story. Friend of mine was involved in an office renovation a few years back, like late 2010s. They took down a wall and discovered an AS/400 machine, we're talking a server from the 1990s. It was running. It was plugged into the network. Nobody knew what the fuck it was doing. It had been walled off for years. Apparently some heroic IT forensics had to be done and it turned out, yes, it was an active part of the infrastructure.