Comment out SQLNET.AUTHENTICATION_SERVICES= (NTS)
in SQLNET.ORA. Now you should be able to connect sysdba, internal, and remote sysdba (if remote_login_passwordfile = exclusive).

General speaking (my experience):
set SQLNET.AUTHENTICATION_SERVICES= (NTS) in Wins
so you do not need sys passwd to start db.

comment out SQLNET.AUTHENTICATION_SERVICES= (NTS)
in Unix, linux so you do not need sys passwd to start db.