Continuing D/L From Different Source

I had almost finished downloading a movie 95.3% when I had to go to work so I turned BitComet off (as the mrs moans about the internet speed being choked when she wants to go on during the day) but when I came back from work the file had dropped off the site I was getting it from.

I have found another site with exactly the same file but I cannot get BitComet to continue it, it just keeps on trying to start again from scratch, at the moment I only have about 40mb to get and dont want to down load the entire film again can anybody point me in the right direction.

I did save the torrent but there are no seeders/leechers at the moment.

Make sure the file and the folder its in s named exactly the same. If not make a backup copy of the file and then rename it to match the new name.

Then bitcomet should take it up