Windows Activation

After I wiped my PC, due to a virus, I receive a message saying 'Activate Windows'. This pops up every 3 hours and takes me out of whatever I'm doing. I have been on Windows support and the people said they cant do anything. I have Windows 8.1 pro now because I got automatically upgraded. Now I have spent over 3 months following all guides and they're all different from what my problem is. I am willing to spend time with anyone who can help me with this VERY frustrating problem!! Thank you to anyone who can respond!

Hi, did you get it shipped with windows 8? You may need to install windows 8 with your original serial and then upgrade manually to 8.1. Let me know how you get on!