Try removing all drives including the boot drive, then just plug in boot drive and reset BIOS, after that check in BIOS that its detected as a boot drive.
Had the same problem on a b85 asrock board, no idea why too. Windows partition was well and intact.
This forum is moderated by volunteer moderators who will react only to members' feedback on posts. Moderators are not employees or representatives of HWZ Forums. Forum members and moderators are responsible for their own posts.
Please refer to our Community Guidelines and Standards and Terms and Conditions for more information.