I am getting a SQL Server error message login failed.

Remember it is the SQL Server login and password that SQL is expecting, NOT an NT one. The default SQL userid and password is "sa" and no password.

It could be a "network" connection problem. If you're registering a local server with SQL EM then register it as "." without the quotes. Try connecting using whichever tool locally on the server without specifying the server name - this forces a local named-pipe connection.

It could be that SQL is out of connections. Check the logerrorlog file for this. Check if SQL has been started in single-user mode. Check the following registry key :-
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMSSQLServerMSSQLServerParameters
Under here there are SQLArg0, SQLArg1...... type parameters - the single-user one is "/m". Remove it if it is there.

Finally, if you're sure that the userid is correct (and remember SQL can be case-sensitive) then try disabling any virus-checking software as this may be interfering.