The disk may now contain lists of criminals, drug deals, politicians paid off, the price of drugs from specific suppliers, etc. I'd take it back to the police and see if they have an expert that can gain access. The data may put you in jeopardy.
I have Acer Travelmate 2300 with a Samsung hardrive in it. A couple of months ago it was stolen and the police recovered it. When it was returned it now asks for an HDD Password. I did not set this and have not been able to log onto it since. Is there any way I can clear this password.