I upgraded my database Oracle 8.1.5 (on Disk A) to Oracle 8.1.7 (Disk B). That works fine. But I found that the listener(executabe TNSLNR) still points to the previous location(DISKA). I tried to modify the path in the registry and I got an error when I tried to restart the listener service.
There seems that by changing he path pointing to the TNSLNR, the listener.ora path is lost as well.
The listener.ora file is in the new $ORACLE_HOME/network/admin. The upgrade create it the correct folder. Still does not work. The problem is that Oracle points to the old $ORACLE_HOME/network/admin. I guess there is an entry in the registry which indicates that, but I don't know which one.