Windows 10 Windows 10 second boot

[Bluetonic]

Hello,

I have 2 hard drives each with a Windows installation and always had the option of booting from either drive upon switching the PC on. I recently reinstalled windows on the second drive using Windows Reset function. Since then, windows will only boot from this drive whilst my other drive is the main one I like to use.

I've been in the bios and pointed the boot process to the drive I want it to boot from and it doesn't recognise it as a boot drive!

I know the windows instalation on the drive is present along with my files and programs as I can browse them when I boot windows from the new installation.

I'm a junior Dev with limited experience in OS. But it's almost like the handshake is failing or the metadata that recognises it as a boot drive. Could anyone shed any light on this please?

TL;DR: Drive A and B have windows. Could boot from either drive. Reset windows install on drive B. Windows no longer recognised A as a boot drive.

TIA

 

[Bluetonic]

Fixed: for anyone who comes across this issue where you reinstall windows on a dual boot system and lose the boot files on the unchanged/untouched system, try this:

Start>settings>update&security>recovery>advanced startup>restart now

Opens options window. Go to troubleshoot and start in command prompt mode.

Find the volume the windows install is on (note this may be different than stated when you click my computer, if so type in DISKPART then LIST DISK. Type Select disk <disk number> then type Detail Disk) .
Come out of DISKPART by typing exit. Type in: bcdboot Z:Windows (where Z is your volume letter)

Reboot - fixed.