This guide is for moving a folder and/or changing the folder name (the method is the same for both) with the torrent still loaded in uTorrent.
1. Stop the torrent by right-clicking it and choosing Stop.
2. Move and/or change the folder name outside of uTorrent (in Explorer, for example)
3. In uTorrent, right-click the torrent and choose Advanced -> Set Download Location.
4. Browse to the moved and/or re-named folder, click OK
5. Optional: If you have re-named the folder and want to change the name of the torrent, so that the new name shows in uTorrent, too, select the torrent and (left-)click it again. (Double-clicking won’t work if it’s set to open the Properties box, or whatever, so take it slow.)
6. Optional: If you want to be really sure you got it right, right-click the torrent and choose Force Recheck. When it stops checking, uTorrent should say that 100% is done.
7. Right-click the torrent and choose Start (or Force Recheck if you want to make sure the torrent does not get queued).