It appears that your hard-drive was legally fore-fitted as evidence in your particular case. Once a case has been dismissed, you must file a return of property notice/motion to either the forfeiture department of the prosecutors office or the police department who confiscated the evidence. Judges are sometimes able to issue an order to return all property seized from you during your criminal proceeding. If you had an attorney in this matter, I would mention your intent to retrieve your hard-drive and see what assistance they can provide to help facilitate the process.