Hello

I will go straight to the issue to save you some time:

I have two 2.5 ATA HDD disks. One (old) Seagate Momentus 7200.4 500GB from an old laptop and one I currently use (5400, 750GB).
I decided I want to use the old one for laptop since it's faster and the 750GB HDD will serve as an external HDD.

So I manually replaced the 750GB HDD with an old one, inserted the Windows 8 installation DVD and the installation started. There were some data on the old Seagate disk divided to 4 partitions so I formatted them all (successfully) and after that tried to remove some of them (I wanted only two partitions). However, this time Windows installation froze so I waited for a long time (20 minutes) and nothing happened. I then (I know I'm dumb) switched off my laptop with the button.

Since then, my Seagate Momentus 7200.4 isn't working. It spins, but is not detected in BIOS. Also, when I connect it to the computer I'm not even able to access BIOS (ironacally, it can be done without HDD, but not with it).

There are no data on the disc since I formatted it, but I would still like to use it as an external HDD if possible. But I have no idea how to recover it. I think only the filesystem of the disc is not recognized or idk...

Any ideas on how to fix the disc?

Thank you very much for your patience and understanding.

Have you tried your 7200.4 drive on another computer?
It is detect into other computer bios when connecting it via sata port?

If drive is not detect in any computer bios then is not just a filesystem issue, if you don't need data just buy a new drive.
Repairing it will cost much more and it wouldn't be safe!

Probably firmware got damaged!

_________________
My firmware database:
https://mega.nz/folder/O01DkBRI

+ michael chiklis.

I think similar that Micael.

test it into another PC to confirm if the problem is from your laptop or is in drive, is the resort is the same in other PC the problem is probably FW problem or heads weak.
in that case If you have no important data waste HDD, because this drive will be problable unstable.