Please help!!

When I created a service using Net8 Assistant on NT the first time, I was able to create it successfully. Then I deleted it and created another. Thereafter, all the other services that I've tried to created gave me this error msg.

ORA-12514: TNS:listener could not resolve SERVICE_NAME given in connect descriptor.

When I attempt to connect to the database, this error shows up.

SVRMGR> connect internal/oracle@oratest
ORA-12154: TNS:could not resolve service name

The paths for listener.ora, tnsnames.ora, and sqlnet.ora are correct and none of them have duplicates exist.

Does anyone know why? Any help is greatly appreciate!