I'm pretty sure it's doing nothing. It doesn't have a monitor so presumably it has a network cable?

It's decades old, so it's a file server? Let's say it's circa 2000, that means it has tiny hard drives that have been spinning for 25 years. And probably a 10mb network connection? With a 25 year old OS?

Sure. Maybe its running Linux from 2001, and the OS is still alive. But without any attention thr disk is long since full of log files. Early 2000s, means this has a few megs (not gigs) of ram, probably less than a couple gigs of disk space, a pentium cpu.

I know it's possible for a machine to be useful and unattended for decades. But in a local library? Frankly I'd just pull the plug.