how do i add part of the file thats already been downloaded

[motorhead]

i started downloading a torrent and got about a third downloaded but my computer f*ed up so i had to crash my comp and reload the OS. but i saved the files from the torrent that had already been DL'ed. now i'm starting to DL the same torrent, is there a way i can add these files and start where i left off or do i have to start all over on the DL?

thanks in advance!

[DreadWingKnight]

http://utorrent.com/migration_guide.php