Windows 10 Make an active partition able to boot

[Computerman]

I have a desktop with 3 hard drives which were all bootable. I added a third drive and now the new drive seems to be the only one that I can boot to. In disk management only the new drive shows boot. The other 2 drives are active and primary. Does anyone know how I can make these drives bootable again

 

[Neemobeer]

Is there an actual operating system and system partition on each drive? Also are these drives using MBR or GPT?

 

[Computerman]

Yes these drives have an operating system, they were booting fine and now they don't have the boot option

 

[Neemobeer]

Are they GPT disks?

 

[Computerman]

Whatever way windows would default format these disks, they were working fine yesterday

 

[Neemobeer]

If they're GPT they don't need the boot flag if they are MBR you would need to add the boot flag back into the MBR. Other than the Windows installer process, Windows doesn't have a built-in method for re-adding this.

 

[Computerman]

If they're GPT they don't need the boot flag if they are MBR you would need to add the boot flag back into the MBR. Other than the Windows installer process, Windows doesn't have a built-in method for re-adding this.

Is there a way to do this and have my programs still work correctly?

 

[Neemobeer]

There are numerous tools to set it, Gparted in a live linux, such as Ubuntu, can set the flag pretty easily. Whether or not the other drives will but is questionable from setting the boot flag.