Windows 8.1 doesn't boot anymore after Windows 10 installation on 2nd drive

I have Windows 8.1 on one drive.

I install Windows 10 on a second physical drive.


Then the computer always boots into Win10. "Ok", I think, before he would always ask which Windows version to boot before, Windows 8.1 was installed on that second drive.

I put the Windows 8.1 drive first in the boot order in BIOS. It still boots Win10.

I press F8 and select the Win8 drive, it still boots Win10.

I physically detach the Win10 drive, it only boots into BIOS...


Can someone help me. I read afterwards that one should remove all other drives before installing Win10. Great.


What I tried after removing the Win10 drive:


bootrec /rebuildbcd

It finds the Windows installation, but when I press Yes, it says "Element not found".

fixmbr brings no changes either.

I tried the diskpart/select as active thing, but it said something along the lines of my drive is no MBR drive.


What did the Win10 installation do to my Win8 installation??? And why??? I don't want to reinstall everything. I can still see all my data and folders when I reattach the Win10 drive and open the File Manager from inside Win10, so it's definitely not that the drive is corrupt, it was working and booting fine before I installed Windows 10.


One goes out of his way to install Windows 10 on a separate SSD and not just a different partition, to make sure that the original installation remains untouched, and then it f***ks up everything anyway!! What happened??

Weiterlesen...