Windows 10 Windows Boot Manager installed to other harddrive with windows on it.


New Member
Aug 9, 2021
I am trying to figure out what happened to my system to prevent it from happening again, and how to fix it.
I had an old hard drive that I got from my family member after I upgraded their hard drive to an SSD for more speed. My plan was to slave it to my computer and format the hard drive, using it as extra storage, since the only problem with it was it was to slow.

I attached it to my computer, then my bios took a lot longer to boot then normal. When the computer reset and boot, it booted into the spinning hard drive instead of my m.2 that was my primary drive. I reset and checked where my windows boot manager was, and it rewrote itself off my m.2 and onto the spinning hard drive. I created a boot option for my m.2, but now its booting off this slow spinning hard drive, significantly slowing my boot times. I have tried all help on the internet, from shrinking the OS and trying to copy the BCD onto the m.2, but nothing has worked. It is saying my m.2 os partition is not active.

Repairing from install media has failed, command line mbrfix bcdrebuild combo failed to fix the problem too. I disconnected the drive that windows boot manager moved to, and attempted the methods above to no avail either. I'm at a loss for what to do, and while I can still use my computer, my boot times went from 2 seconds to well over 1 minute. Has anyone run into an issue where the slave drive takes over your main drive, rewrites your boot manager, and then deactivates your old OS partition?

Any help would be appreciated.
The Windows installer is a bit dumb and from what I've seen will typically install on the first disk is detects regardless. The tried and true method would be to remove/disconnect all drives you don't want Windows to install on and install. It is possible to create a boot partition on the intended disk but is quite a bit of work.
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