Looks like you have Windows 10 installed.
Go to MSCONFIG:
Use the keyboard shortcut “Windows Key + R” and the “Run” window will open. In the text box, write “msconfig” and press Enter or OK and the MsConfig window will open. Also, in Windows 10, Windows 8, you can open the Run window from the shortcuts menu in the bottom left corner.
Then go to "BOOT" then click on "ADVANCED OPTIONS". Under the "Number of Processors" input "8" or the amount of cores your CPU has. Reboot and see if it shows all 8 cores running.