[HELP] "Reboot and Select proper Boot device" with 2 drives.

piltenko · August 2, 2020

Hello! Sorry for the long post...

I had my 250GB SSD. I bought a new 1TB SSD, connected it to PC, installed Windows 10 on it using the bootable USB, copied a bunch of files from the old drive (1TB being C drive and 250GB showing up as D drive). When both drives are plugged - i can choose which one to boot from (attachment #1), with "volume 4" being Windows on my 250GB drive and "volume 7" being Windows on 1TB drive. Windows from 1TB drive boots normally and everything works fine, i'm writing this post now while booted from the 1TB drive.

Now i unplugged the 250GB drive (i intend to wipe it out and sell it) and tried to boot only having 1TB drive plugged in. And it didn't boot, it says "Reboot and Select proper Boot device" (attachment #2). Plugged the 250GB drive back in and it showed the OS selection screen again (attachment #1) just as before. It's as if whatever causes PC to recognize that the drive has OS on it is located on the 250GB drive, but not on the 1TB one.

I thought the issue could be the lack of the "EFI System Partition" on the 1TB drive (attachment #3) so i created it using diskpart utility (attachment #4). But it didn't work, as soon as i detach the 250GB drive (so only 1TB drive is plugged) i get the same error (attachment #2).

I tried different boot order options too, didn't work, even when i set this 1TB drive as the priority (attachment #5). I tried inserting the bootable flash drive to access "Startup Repair" but it said that it couldn't do anything.

I really don't want to reinstall everything on my 1TB drive again. Does anyone have any ideas? Thanks!

C2dan88 · August 2, 2020

Windows wont add multiple bootloaders if it detects an existing one on another drive. You should only have one drive connected whilst installing windows so it does go about adding random crap to other drives during installation.

Disconnecting all drives and creating a new efi bootloader on the 1tb ssd using diskpart should fix this issue.

https://www.tenforums.com/installation-upgrade/52837-moving-recreating-efi-partition.html#post698505