sa user is locked out and login fails with Windows Authentication. Now what?

I am logged in to a Windows 7 computer as an admin. I am trying to connect to SQL Server 2012 on the same machine. The SA account is locked out. When I try Windows Authentication, the login fails.

How do I log in now? Is there an external tool to unlock the SA user? I used an external tool to change the SA password. I don't want to reinstall the software.

Read and follow the steps described in Connect to SQL Server When System Administrators Are Locked Out:

• start the server in administrative mode with -m or -f
• connect as a LUA elevated process (runas administrator)
• create a login for youserlf and add it to sysadmin group