Problem solved by reinstalling the SQL Server installer is very straightforward and inflexible.
Create a backup of database, backup of logins with the following article: https://support.microsoft.com/en-us/kb/918992
(it describes a procedure, the execution of which will generate T-SQL code to create the logins). Delete the old dB instance, set a new, restore the logins obtained above code will restore the database from backups.
Not as difficult as it may seem.