4 cores should show up in task manager/cpu-z. If not I would check to see that the board is running a BIOS with support for your cpu. It may not be at the moment. If it is running a BIOS that officially supports it I would then look around the BIOS to see if there is a option to disable/enable cores. Make sure if that is there that its set properly.
While you are at it make sure all your drivers and everything else is up to date as well. http://www.gigabyte.com.tw/Support/Motherboard/Driver_Model.aspx?ProductID=2982#anchor_os
Win7 Does not add cores per demand.
Being new to Win7 is no big deal. If you know how to use older windows OS's its the same thing for the most part.