Hi!
First of all, remove the HDD and put in a known working HDD or a new HDD without any files on it.
Does the Xbox show an error now?? If yes, then the HDD is broken and need to be replaced.
If not, then it’s most likely the motherboard.
Please try another known or new HDD first! Please let us know how it goes! Then I can share guides regarding partitioning and installing the new HDD.
Thanks!