The server principal 'username' already exists.

I've removed the username from the Security/Logins. Now I want to recreate with the following code.

CREATE LOGIN [USERNAME] WITH PASSWORD=N'Ir5zfuLcdZWDZUyqZPdPBRtItc/cnqxBPAcTUITzoc=', 
DEFAULT_DATABASE=[master], DEFAULT_LANGUAGE=[us_english], 
CHECK_EXPIRATION=ON, CHECK_POLICY=ON

And I kept getting this error:

Msg 15025, Level 16, State 1, Line 6
The server principal 'USERNAME' already exists.

So I ran this code:

SELECT name  
FROM master.sys.server_principals
WHERE name = 'USERNAME'

And in the 'name' column it does show 'USERNAME'. So I am assuming this means the user 'username' was not deleted from the master.sys.server_principals table, correct? If so, how do I totally remove it so that I can recreate them?