Here below the steps for resolving the login error of Sql Server.
Go to security tab under your database.
Click to expand the Users tab under security.
Find weather NT AUTHORITY\SYSTEM is present.
If not, Right click on users, Click on new user
In new user window, general tab change the user type to windows user.
Select the User name to, NT AUTHORITY\SYSTEM you will have to find it in the Advanced tab, find now, and select system.
Similarly for login name, browse and find NT AUTHORITY\SYSTEM.
And in the membership tab to the left, select all the required boxes except db_denydatareader and db_denydatawriter and click ok.
