Wa alaikum assalam,
It is a good sign that you feel disturbed about what happened. That shows your conscience is alive. In this situation, there are two separate matters:
First is the sin of stealing. For that, sincere tawbah (regret, stopping the act, and firm intention not to repeat it) can be accepted by Allah.
Second is the right of the owner. When someone’s property is taken, their financial right remains until it is returned. The right of the owner — is not automatically cleared just because you gave money to a poor person, because the hard disk belonged to that owner, not to you.You had no authority to decide that its value should go to charity. Charity does not cancel someone else’s financial right.
So yes, as long as the owner has not been compensated for the hard disk, the matter is not fully settled.
You do not need to publicly expose yourself. But you should find a way to restore the owner’s loss — either by returning the hard disk if possible, or by compensating him for its cost in some discreet way. Once the owner’s right is fulfilled and you have sincerely repented, then inshaAllah the matter is closed.
Allah forgives those who correct their wrongs. The important step now is to complete the correction properly and not repeat such a mistake again.