SQL Server 2012 has SQL Server Configuration Manager tool. Choose from OS Start-> All programms->Microsoft SQL Server 2012->Configuration Tools->SQL Server Configuration Manager.
In configuration window list SQL Native Client and click on Client Protocols. If last column has all values as Enable it is OK.
Click the SQL Server Services.
Right click the first row and select Properties(Właściwości)
In Properties window in Log On tab you see:
Check Log on as on Built-in account. From List select Network Service.
Click the Apply(Zastosuj). In Confirm window agree on restart clicking Yes(Tak) button.
Second row in the same way, set in its Properties window in Log on tab as Loca lService.
List SQL Server Network Configuration and click the Protocols for SQLEXPRESS. On the right panel you see for TCP/IP and Named Pipes Disable status. You must change them on Enable.
Right click the Named Pipes and choose Properties.
Select from Enabled list Yes. Click the OK button.
In the same way change Enabled status for TCP/IP. Right click the TCP/IP and choose Properties.
You see in Protocols tab Enabled as No.
Select from Enabled list Yes.
Click the Apply(Zastosuj) button. In Warning window click the OK button.
Then go to IP Addresses tab. In it you see all Enabled field as No and empty TCP Port.
Change all Enabled as Yes. And in all TCP Port field write 1433. Either in IP4 section write in IP Address 127.0.0.1, if you work locally.
Click the Apply(Zastosuj) and in Warning click the OK button.
List SQL Native Client and click Client Protocols. Right click the TCP/IP and choose Properties(Właściwości).
In Protocol tab you must set Default Port as 1433 and Enabled as Yes.
Click the OK button.