After the installation of the Oracle software, did the Database Configuration Assistant (DBCA) successfully create a database for you? There is no mention of a database being created in your explanation of the problem so the reason you may not be able to connect to a database is that one does not exist. Another reason I mention this is because the subdirectory mentioned in the error message is one used by the DBCA to store templates. Depending on how you asked the DBCA to create a database, if it cannot store a template from which to create a database from, it may not be able to successfully create a database.
Check the Services panel to see if an Oracle database service has been created. If it has, check the oradim.log file to see whether the service started up successfully. If it has, check the database alert log to determine whether the database creation was successful and whether the database has been opened. If these checks are all successful, it could be that the scott schema does not exist in your database. Log into the database as the SYS user as follows to check for the scott schema:
sqlplus /nolog connect / as sysdba select * from dba_users where username='SCOTT';
If this returns a row, then the scott schema does exist. At this point, it could be several issues. The scott password is locked (review the previous SQL output to see if ACCOUNT_STATUS is LOCKED), or the password is not tiger. If the account is not locked, issue the following command to change the password:
alter user scott identified by tiger;
This was first published in May 2006