Oracle 9.2.0
Windows 2000
Trying to connect to Oracle server (from the server itself).

Windows user is a member of ora_dba group, and also in local admin group. Plus in sqlnet.ora file, the authentication is set to NTS.

However, I can't connect to Oracle server when login as windows user w/o providing a password. What I did was:

c:> sqlplus /nolog
sql> connect /as sysdba
ORA-01031: insufficient privileges.

So what went wrong here? I feel I've set everything the way it needs to be, but just can't get it work.

FYI -- the Oracle was installed when I logged in as administrator to the local machine. And now I'm log in as a domain user. Of course, both local admin and the domain user are member of ora_dba and local admin group.

Any hint is greatly appreciated!