To restore the drive to its original capacity you need to remove HPA on the target drive:

1. Download ISO image from http://www.hitachigst.com/ under Downloads & Utilities -> Feature Tool -> CD Image;
   
2. Burn the ISO image to a CD according to the rules described at http://www.petri.co.il/how_to_write_iso_files_to_cd.htm

3. Boot your computer from the created CD;

4. You will get the "Drive list" window after the boot process is finished. Select the necessary ("broken") hard drive from the list using your mouse or arrow keys;

5. Click on the "Features" menu or press Alt-F keys and select "Change Capacity";

6. You should see "Manufacturing values" and "Current values" on the appeared window;

7. Click "Options" and choose "Maximum Capacity" from the list. The appropriate value will be automatically entered in the "New Capacity" field;

8. Click OK.