Connection Problem with SYS user

Oracle Version : 10.1.0.2.0
OS : Windows XP


Not Able to connect to database with "SYS AS SYSDBA" user

ORCL@TAJ>conn sys as sysdba
Enter password:
ORA-01017: invalid username/password; logon denied

AND
ORCL@TAJ>conn sys as sysdba
Enter password:
ERROR:
ORA-01031: insufficient privileges

AND
ORCL@TAJ>conn / as sysdba
ERROR:
ORA-01031: insufficient privileges

Note: When OS is member of ORA_DBA group and SQLNET.AUTHETICATION_SERVICES=(NTS)




Suggestion:

RECREATE PASSWORD FILE

C:\>ORAPWD FILE=C:\ORACLE\PRODUCT\10.1.0\DB_1\DATABASE\PWD[SID].ORA PASSWORD=PWD
ENTRIES=5 FORCE=Y --- When Passwordfile already exists