Guessing here, but here's my idea anyway:
You've applied the icon with the Get Info Finder window of the icon you wanted to apply, and then clicked on the little ICNS picture in the top left hand corner, and copy and pasted this onto the hard drives' Get Info windows, I'm guessing?
This takes the icon for an ICNS (Apple Icon file), which is the page-like icon, and places that on the hard drive. This does not move the icon itself, but just the icon for an ICNS.
To apply an ICNS, open it using Preview. Then Select All (Edit > Select All), select Copy, then Paste this into the Finder's Get Info window for the hard drive.
Hope this helps.
PS If all else fails, opening the Get Info window, clicking on the new icons, and pressing delete will revert them to their original icons.