Which format are the files, you downloaded? Mpeg1,2, DivX etc. Maybe you have to convert the Files. What Home-Cinema-System do you have? Which File-systems are supported?
I usually download video torrents that are .VOB files, and since I'm cheap and refuse to pay for a good quality burning program that will burn these without converting, I run the files through the aptly named, "Convert VOB to AVI". Seriously, that's what the program is called.
From there (Its usually about 4 or 5 .VOB files), I place the new .avi files in DVDFlick, and customize/burn from there.
All 100% free.
I had my first experience with .mts files today, which are from HD cameras...I torrented the Sheffield HD DVD, and converted the .mts with "Prism Video Converter" and then imported the titles into DVDFlick.