hmm.. don't you need this too to make it work? [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.torrent] @="uTorrent" "Content Type"="application/x-bittorrent" so a complete .reg would be something like: Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.torrent] @="uTorrent" "Content Type"="application/x-bittorrent" [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\uTorrent\shell\open\command] @="\"C:\\Program Files\\uTorrent\\utorrent.exe\" \"%1\"" didn't work for me before I added the .torrent class