Cannot connect to Sql server - help

Hi,
I used to work with Sql server 7.0 and my connection string was:
Provider=SQLOLEDB;User ID=sa;Password=;Initial Catalog=Eldat_DB;Data Source=YOSSIBA

After clean unregister and installing Sql server 2000 Using the same connection string I get the error:
Login failed for user 'sa'. Reason: Not associated with a trusted SQL Server connection.

After removing 'sa' I got the error:
Login failed for user 'yossiba'. Reason: Not associated with a trusted SQL Server connection.

My configuration of the server was wrong?
How do I know Provider,Use ID,Password,Data Source parameters?
Please adviseI think you need to chek the connection string with respect to the logins on the server.And the corresponding frontend too.|||Originally posted by harshal_in
I think you need to chek the connection string with respect to the logins on the server.And the corresponding frontend too.

Hi,
When I entered EM..right click on the SQL Server | properties
I have noticed that under Security Tab 'This Account' is marked and the Domain and name are correct but the Password is not the same password I enter to my computer (it is longer).
Trying to change the password won't let me althogh I am registered as an administrator.
In addition to that the Authentication was Windows only, changing it to Sql server and Windows with sa and my computer password raised me and error: Login failed for user 'sa'.
Can that mess be cleared?
Thanks