SQL Server 2008 R2 - Unable to delete Login
Short intro

To connect to the server you have to have a login to access the server. To access a database you have to be a user in that database. All Logins are member of the server role public which can access the master database.

So to find users to drop within a database you query sys.database_principals and to find logins sys.server_principals. When you drop a login it's not removed from the user list of the databases and the SID is there until you drop the user.

So henryhr exists as a user in the master database but not as a login on the server so try use master; drop user henryhr; to drop the user henryhr from the master database