Here's my problem.
My processor is i5 6600k overclocked to 4Ghz, and my mobo is MSI Z270 Gaming M7 updated to newest bios.
Widnows sees only 2 cores instead of 4. I tried msconfig, there are only 2 cores to choose.
I tried CPU-Z, it shows only 2 cores and 2 threads.
I tried doing something in bios, everything in bios is looking ok. (It shows that all cores all enabled, and shows number 4)