@thedude - you can let your computer shutdown by entering this in the "run this program when the download finishes" textbox in the torrent properties:
shutdown -s -t 30 <-f>
the delay after -t may be shortened, but i usually put 30 just in case I'm doing something else while the download finishes. If it warns me that it will shutdown in 30s, all i have to do is type shutdown -a to abort shutdown and continue my work. the -f parameter may be omitted if your running apps recognize a shutdown command properly. Chikka is a problematic app, you might need -f if you want it closed by force, otherwise, the PC will be stuck at an "end task" dialog, waiting for your input.