The torrent history is saved in resume.dat stored in %appdata%\utorrent.

A quick solution is to move the partial files (if you want to store on your new HD of course) then the folder %appdata%\utorrent to the new HD. Then you edit resume.dat with http://forum.utorrent.com/viewtopic.php?id=31306 by using the function ‘find/replace’ to change the path or drive letter if something changed.

Then you start uT, it should resume your torrents.