Well, when I installed Windows 10 to my PC, HDD was there, everything functioned normally, but the problem “boot into BIOS” occurred on the next day. The problem is the disconnection between the BIOS and HDD is not permanent, it only happens when I shut down the pc and turn it on after an hour, but when I did one of the 4 options in the description, the connection will come back and remain for the whole day, so I can’t identify what is wrong!
well, that's what i believed so I replaced the CMOS battery 3 weeks ago and that didn't help. Today I ve just turn pc on by pressing 2 buttons: 1/power button (it goes to BIOS like that) 2/Reset button (then Windows starts normally). it's not a big deal but there's obviously something's wrong. thanks anyway.