It's not very hard you can do it easily by yourself.
Go to the Volume Control window where you adjust the volumes in windows
Select that you want to record sound from either Stereo Mixer or Wav
Download a program which can record longer soundfiles
I use Jet-Audio and then play the movie in get media while recording sound in Jet-Audio (or other program).
I'm sorry if this sounds a bit confusing, I'm not used to explaining technical things in english.