I'm dual booting two windows 10, bootgmr issue

ashramnavivi said:

If I get new M.2 SSD and get a fresh OS on it, after plugging back the old SSD and HDD, would I have to format them or not?

You wouldn't have to but should at least clean them, delete unneeded partitions and merge them with existing partitions for more space.

ashramnavivi said:

I marked my SSD's C: drive as Active now, I will now restart my computer and unplug HDD and see if it boots properly.

https://i.imgur.com/q64K0Na.png

- - - Updated - - -

Dude... I can't explain you how much happy and thankful to you I am right now

https://i.imgur.com/9oxhmvw.png

Seems like that the problem has been solved, but I still need to see how to deal with my old HDD that I still want to use as external one (I would just remove Windows folder or something)

Where is your UEFI partition, shouldn't there be one ?

ashramnavivi said:

I don't know...

All I've done is marking SSD's C: partition as active then unplugging HDD's SATA connector.

- - - Updated - - -

Also, my SSD is MBR

- - - Updated - - -

Also, I'm not sure what should I do with my old HDD, can I still plug it back in and use it as my second drive or something? I would use it externally (most likely)

Sure you can, just make sure that BIOS is set to boot from SSD first. After that you can clean HDD up by deleting windows and unneeded partitions which you can merge in one.

ashramnavivi said:

After I again plug back my old HDD in, should I go to msconfig and remove it from the Boot tab?

Yes, definitively.