Today I had problems with logging in to my newly installed SQL Server instance. During the install i choose “Windows mode” but I did mange to mess up which user that has access to SQL Server. I tried to start up in Single user mode which did not work, but I found this blog post that had a great solution:
Basically these steps:
1. Install PSExec
2. Open the command line with “Run as administrator”
3. Run this command: PsExec -s -i "C:\Program Files (x86)\Microsoft SQL Server\110\Tools\Binn\ManagementStudio\Ssms.exe"
This will open SQL Server Management Studio as the NT AUTHORITY\SYSTEM-account which has all the privileges needed.