I downloaded and installed Oracle 9i. When i logged on to SQL for the first time, i got ORA 12560: TNS protocol adapter error.How do i correct it?

I searched for the tnsnames.ora files and found 3:

1. tnsnames.ora.sample in C:\oracle\ora90\hs\admin
2. tnsnames.ora in C:\oracle\ora90\network\admin
3. tnsnames.ora in C:\oracle\ora90\network\admin\sample

Do i need to make any changes in the ORACLE_SID,ORACLE_HOME and TNS_ADMIN parameters here....and if so what kind??