download and reinstall widows 8 to my dell inspiron 15R

I had a problem with my windows 8 and i tried to repair and restore but it didn't work.

I downloaded windows 8.1 from Microsoft website and i had to reset my windows.

Now my windows is not activated and windows key is injected to motherboard so i cant use it

please help me how can i solve this problem and where can i download windows that can use my product key?

Best regards,