If you see the thumbs up and thumbs down on the top right of each post that means its a discussion thread, not a question thread, and therefore cannot have a best answer selected.
That explains it. Sometimes it is a bit hard to notice the difference between a "discussion" and a "question" thread after it has been created.
Sorry to hear about your problem. Did you get it resolved?
Hello again WR2, I hope everything is fine? The problem did get away after applying the latest BIOS updates (possible solution) but also at the same time tighten up all motherboard screws. They were not lose, but it was possible to secure them more. After that the resets has not been seen again. Since they were very inregular I was not sure for a long time the problem actually was solved.
I've changed it to a 'question' type thread. You will now be able to see the best answer button.
Thanks a lot, I have now given the Best Answer to a user in the thread.