Firstly start the torrent in utorrent and let it be ON for a while wen it starts downloading it, stop that particular torrent.

1) go to the path where bit commet has saved the actual file that you were downloading.
2) Just copy the file from there to the directory where utorrent is downloading the file..
3) if u paste in the correct directory, windos will ask u to replace the file..
4) Once replaced, go to utorrent.
5) right click on the torrent and select "force recheck"
6) once its done checking, start the torrent...
7)If ur torrent wud hav been downloaded correctly in bit commet, and there are enough seeders, utorrent wil download te remaining part..

One more thing, start using utorrent


EDIT:- Quote Removed.Sorry got mixed up..