developer/2000 2.0 questions

I'm new in Oracle, so help me please.

[Quoted]
1. So, I've installed developer/2000. When I tried to build database, I was asked to enter password for user 'system'. Where I should know this password from? Is it 'manager'?
2. When I tried to use SQL Plus and was asked to enter user name and [Quoted] password, I enter 'system' and 'manager'. Then I received this error:

 ORA-03121: no interface driver connected - function not performed

[Quoted] Can you explain me the reasons of this error?

3) I has scripts for my own database. How to build this database using developer/2000?

Thank you in advance.

-- 
Mindaugas Vieraitis
e-mail: mindaugas_at_nm3.ktu.lt