Option 1:
1. Right-click torrent, relocate or move data or whatever it is. Don't move single files - move all of the data in the torrent.
Option 2:
1. Stop and remove torrent from client.
2. Using Explorer, move all data into a directory on your external (say F:\Downloads).
3. Load the torrent, change download location to the directory you had above (F:\Downloads). Do not descend into the folder in the torrent. Start, and then stop if it doesn't automatically recheck (i.e. if it starts downloading). Force a recheck, then resume it.