SCO doesn't have a "5.1" release that I'm aware of, but that's probably not important. The 1/42 designation would indicate a full disk on the root (main) filesystem. As VodkaDrinker stated, this can be caused by a log file which has consumed a great deal of space. It can also be caused by any number of issues, such as using an incorrect device name for a backup destination.
If you can gain access to the system, I would start by clearing (DO NOT REMOVE) some log files you don't care about (such as /usr/spool/lp/logs/requests), then start looking around for very large files.
You can look for large files with a find command:
# find / -type f -size +400000 -print
That will display files larger than 200MB. Adjust to your needs.
"Proof that there is intelligent life in Oregon. Well, Life anyway.