I turned off my second core and I don't know how to turn in ON ..

Hello , I made the mistake to turn off 1 of my cores .. I am with Intel(R) Pentium(R) CPU B980 2x2.40Ghz .. I misslicked something in msconfig ... God I don't know what I was doing there and now when I start my Task manager it shows only 1 core .. Please can you tell me how to turn my second core again .. Not from msconfig / boot / advanced options (this is only for the start of the windows)