Please see this article about Vista:
http://audacityteam.org/wiki/index.php? ... s_Vista_OS
If you look especially at this section of it:
http://audacityteam.org/wiki/index.php? ... nel_issues
there is a grey panel "HELP WITH RECORDING COMPUTER PLAYBACK OR STREAMING AUDIO". Set your Windows Control Panel to record from the appropriate device meant for recording the computer output, then Audacity should record from it when the recording device in the Audio I/O tab of its Preferences is set to "SoundMapper". This "SoundMapper" choice uses the current device set in the Windows Control Panel.
Unless you only want a few minutes of the DVD audio, it's not a very good idea to extract the audio off a DVD by recording it playing off the sound card. It is prone to errors because you are converting
it to analogue to play it and then back to digital when it enters Audacity, and obviously it is a real time process (if the DVD lasts an hour, it takes that long to record the audio).
Try and extract a digital copy of the audio in preference as this
only takes a few minutes. This can be done with many video editing
programs if you have one, or there are other tools that provide a simple interface for extracting the DVD audio and converting it to WAV, AIFF or other audio formats.
What you have to do with these tools is to drag the VOB files off the DVD into the program and then choose the audio-only output format you want e.g. WAV for perfect quality, MP3 for a much smaller file if you don't mind some minor quality losses. A simple tool to convert the audio from VOB files to WAV or MP3 is SuperPlayer, for Windows:
http://www.erightsoft.com/SUPER.html#Dnload
Note if you can watch the DVD on the computer you should also be able to watch the VOB files (which contain combined video and audio) directly from the computer hard drive, using the same software you use to view the DVDs. If your software can't do that, install the free VLC player:
http://www.videolan.org/vlc/
If you are trying to extract the sound digitally from a commercial DVD it will probably be copyright protected so you may get an error in SuperPlayer. In that case you'll have to use a DVD decryption tool to remove the protection from the VOB files. Try
DVD Decrypter:
http://www.soft32.com/Download/Free/DVD ... 586-1.html
You can then if necessary use Super Player to convert the decrypted VOB to other audio formats.
Note that DVDs have a number of VOB files on the whole DVD and if you want the whole audio off the DVD, the converted WAV or MP3 files would have to be joined together (you could do that in Audacity). Super Player can only take the VOBs you give it, but DVD Decrypter and other similar tools can be configured to select the parts of the DVD you want (or all of it) to make just one VOB. They can also make an audio only file for you, but this will probably be in AC3 format. Audacity can't play that format directly, but Super Player can convert it to WAV or MP3.
Decryption tools will also of course work on unprotected DVDs, and if you frequently want to take the audio off DVDs, they will make life a lot easier for you.