Failed to start up after removal of unused hard drive

[4-null-nan]

When I removed an un-used hard drive, I couldn't start up Linux. I wonder if there is a small chance that I did use that hard drive as a boot sector or something to that effect.
I did try to boot up using a gParted disc and I could mount and see the correct hard drive is in the computer.

The error was invalid file system or something like that, and falls back to grub.

I put back the other hard drive and it boots up successfully.

How would I fix this? Is it by any chance that the two hard drive IDs are generated differently when both are in there and cause problem?

I would like to have a choice of removing the un-used hard drive if I need it for something else. Thanks.

[CelticWarrior]

I would say the chance is huge, not small.

BIOS or UEFI? The instructions are different.

[4-null-nan]

The setup is BIOS.

[CelticWarrior]

So the bootloader is at the MBR of the drive you removed.

Boot with both drives and simply install Grub to the one you want to keep.

[4-null-nan]

Great. Thanks. It works now after install the grub on to the correct drive.