Cannot connect to DB error

[KENNETH JANUSZ]

I have installed 9.0.1 on my Dell PC with XP Prof.   When I installed it I installed the demo DB and everything worked fine.  Now I have installed a second DB and I cannot connect.  I made changes to listener.ora and tnsnames.ora as recommended by others on this list.    I also added the IP addresses to the HOSTS file as such: 127.0.0.1    localhost (original entry) 127.0.0.1    DC0X4411 (Oracle generated name for KEN db manually added) 127.0.0.1    PARTS (new DB name manually added)   Here is what I get when I try to connect.   KEN database - Oracle generated name is DC0X4411 ORA-12154: TNS: could not resolve service name   PARTS database ORA-12541: TNS: no listener   Any help I can get to solve this problem will be greatly appreciated.   Thanks much, Ken Janusz, CPIM