Never enabled Hyper-V.
Tried to run HWiNFO32 instead of HWiNFO64 - the same result (no second CPU).
Uninstalled KB3042085 and KB2976978, disabled all antiviruses/HIPS, restarted system, - nothing changed.
Rollbacked the whole system (have an old back-up image) - the issue disappeared (HWiNFO64...
Thanks a lot for such a great monitor.
Using HWiNFO I have never had any issue until today when updated my Windows 8.1 Pro x64.
Installed only 2 updates:
1) Update for Microsoft Windows KB3042085
2) Update for Microsoft Windows KB2976978
And the second processor including all sensors...