To gain control of a SQL instance if the user is an Admin on the machine but not in SQL Server

1.        Stop SQL Server service if it is running. 

2.        Set the start up parameter to “-m”.  Do this in the General tab of the service.  Remember any pre-existing start-up parameters so you can restore to the original configuration later.

  

3.        Start service.

4.       At a command prompt:

sqlcmd

create login Paul WITH PASSORD = 'hello!1' 

go

sp_addsrvrolemember 'Paul', 'sysadmin'

go

Note:  SQL has default strong password policy

5.        Put back to normal user mode

remove -m

stop service

start service