Red Hat Enterprise Linux 2.1
The server was powered down gracefully, moved to a new rack, and then powered on.
Ran a fsck from the rescue environment and it eventually completed, but the server would not boot properly.
The hard drive was in the process of failing, so it was replaced and the operating system was installed onto the new disk. The old disk was stable enough to be mounted read-only, and much of the data was salvaged.