I think I tried that but ill look at it again. Makes my newish laptop look like I'm running a beta.Hi, i had the same issue when i installed 8.1 on one of my computers.
What fixed it for me was:
1.- go into your bios, and disable secure boot
2.- restart & let windows start
3.- Restart again, go to bios an enable secure boot again.
After this, the message was gone.
Hope it works for you too