OSQL didnt like rookies

Sory for fullish question,but i'm coming from DB2 and Oracle world,and not SQL world.
How I can understand,OSQL utility is command-line utility in SQL server.So,I tried to start it,but it failed with error:
Login failed for user 'Administrator'. Reason: Not associated with a trusted SQL Server connection.

There is some properties for my sqlserver:
Authentication is "Windows only".User Administrator is admin on machine.In Windows services,there is one servis ( started) and logon for that service is Administrator.In fact,my SQL server works fine,because other GUIs works ok.
SQLSERVERNAME=hostname=navtest.
I tried to logon by entering in cmd this
osql -S NAVTEST
but every time I see error :
Login failed for user 'Administrator'. Reason: Not associated with a trusted SQL Server connection.
What i am doing wrong?
Every help will be greatJust because the sql service runs under the Administrator's account doesn't meen the Administrator can log onto the SQL Server.

By default, the Microsoft SQL Server setup creates the "BUILTIN\Administrators" login, which gives any account in the Local Administrators group system administrator (sa) privileges. Most people delete this account, could be the problem you are facing.

You can add the local Admin account back and grant that account sa privileges.|||Thanks,Paul!
I entered osql -s <servername> -E and it works!
Now,I tried to enter some commands,but I don't know how to end it.
I tried this:
1> select * from northwind......
2>
3> /
4>

Now,how You say to SQLSERVER execute commands?

Thanks a lot,Zvonimir|||hum... when you tried the -E what userid had you logged in with?

go terminates a block of commands.|||I find that switch -E by searching this forum...
And GO really works!!!

Thanks,Zvonimir|||Could have also found it by looking in Books Online. You can also change the command terminator with the -c switch.

btw, what userid were you using when you had success with the -E switch, Administrator?|||-E switch explicitly specifies your intent to log on using trusted connection. The default behavior for OSQL is to use Standard SQL Server Security. That's why Z was getting his(/her) error at the beginning. With -E switch the logon succeeded using security context of the currently logged on user, - Administrator.