Using BootIt BM, some years I had my computer dual booting Windows 7 and Windows 8 (updated to 8.1), but I never liked Windows 8 so I kept using the Windows 7 entry. During the free Windows 10 upgrade window I upgraded the Windows 8.1 partition to Windows 10, but continued to use Windows 7.
Today I decided to work with Windows 10. I was able to boot, and went through many Windows Updates (requiring many restarts). After one of these restarts I saw a message from BootIt BM about an unrecognized partition (which I ignored). Everything still seemed fine in Windows 10, and I rebooted manually several times.
But then I tried to reboot again into Windows 7. The computer will not boot (just a single beep). And now if I select Windows 10, the same thing happens.
What to do?