Demantra 7.3.1 installation

Hi ,

 I am trying to install Demantra 7.3.1 in Windows server 2003 enterprise edition. When i give the db username,password and TNS name of the database , i am getting error as follows

 When i use "sys" user  i am getting error as

 "connection refused" ----Failed to establish administrator connection to database.It may indicate incorrect jdbc settings or incorrect username or password

 When i use the "system" user i am getting the error as

  "incorrect password" ---The entered user's password is incorrect. When i click next it throws the error as

   "SYSDBA PRIVILEGES"----The user does not have sys dba privileges.