Question Dual Boot. Formated original win8.1 now my Win10 wont boot


Jan 7, 2011
Hello, having a strange problem. I was using Win 8.1. Decided to try Win 10. I installed Win10 on 2nd SSD. Using it as dual boot because was unsure if I'd like Win10. I recently decided to format my 1st drive with Win8.1. Now my PC is acting as if I don't have a bootable drive or an OS. But my Win 10 is fine and unchanged on a separate SDD. Any idea on how to help? Yes, I have changed the boot order to the SSD with Win10 but Nope. It's as if It never had Win10.

"Reboot and select proper boot device or insert boot media in selected boot device"


You probably had system files on the other drive, boot off a Win 10 setup media and try doing a repair setup to put back the missing files. I'm guess you installed Win 10 on the drive with the other drive connected which often causes this issue.


Win 10 Master
When you installed win 10 on 2nd drive, and still had win 8.1 in the PC as disk 1, WIn 10 has added itself to your boot partition on disk 1. That is what is meant to do if it finds a boot partition.

Downside is when you remove disk 1 or format it, disk 2 can no longer boot. Making it 1st in boot order doesn't help as it doesn't have the files the bios is looking for.

if you have a win 10 installer, can you do this
Boot from installer
On screen after language choice, pick repair pc, not install
Pick troubleshoot
Pick advanced
Pick Command Prompt
Type diskpart and press enter
Type list disk and press enter
this will show a list of disks attached to PC, select the WIn 10 disk by typing
select disk X (X being number of disk)
type list part and press enter
this lists the partitions on the drive, can you show us a photo of this? Upload to an image sharing website and show link here.