Please,I have problem!

On my host( win200) ( who is running Oracle 9.2) I created OS user RGFI.And,under Oracle database I created user RGFI authenticated
Also,I set OS_REMOTE... init parameter on true.Also,I set OS_PREFIX on "" ( which means no prefix).I checked user from table DBA_TABLES,
it show me correct username and password external,it is ok!
Now,every time I tried to connect to my db by user rgfi through SQLPLUS
I see error:
Invalid username/password.
I believe my db think it is user under database,no external user.

My question:
How can I connect to db through SQLPLUS with OS account?
Is there any manual about step-by-step configuring for Oracle?
And of course,what I am doing wrong?

Thanks for advice,Zvonimir