It sounds like Oracle still thinks he's up. As Sam said, make sure your environment variables are setup correctly. You can set them by sourcing the DEMO.env file probably in /app/oralmc/demodb/816.

If that doesn't work, start svrmgrl, connect internal, and shutdown abort. Then look for $ORACLE_HOME/dbs/lkDEMO. You can then remove this file (or move it to another file) and try to start your db.

Also, make sure your concurrent managers are down while your are doing all this...