How To Disable Opera’s BitTorrent Client?
To disable Opera’s BitTorrent integration, type about:config in the browser address bar and search for BitTorrent in the quick find, once you see the option click on the BitTorrent text to open the preferences. Uncheck the box that is next to enable and click on the save button to disable the integrated BitTorrent support. Once you have done that Opera will treat torrent files as regular downloads.