Ok, this guide covers how to simply copy a extract the audio from a video DVD to a audio CD. The resulting quality should be excellent, almost as good as the original DVD sound quality. The tools you will need installed are:
DVD Decrypter 3.5.4.0 (no longer being developed for legal reasons, but can still be downloaded)
Nero 6 Burning ROM
Nero 2-Channel AC3 Input Plug-In (install after you have installed Nero 6)
Part 1: Ripping the DVD with DVD Decrypter
Start DVD Decrypter, go to "Mode" and select "IFO".

Once in IFO mode it will automatically select to copy the longest part of the DVD (so extras, into videos etc wont be included). You should not need to change this from the default. However, occasionally the first or last track(s) may just be credits, into videos etc, in this case, you will need to uncheck the boxes for those tracks.

Once done, uncheck all boxes except one audio track, normally it will be a AC3, but it could also be a WAV or MPA file, it must be 2 channel only, surround is not supported. If there is more than one 2 channel audio file, go for the first one on the list, the others may be directors commentaries etc. Once you have selected the correct audio track, select it, and then select the "Demux" option instead of the "Direct Stream Copy" option.

Go to the "Tools" menu and click "Settings".

Click the "IFO Mode" tab, leave all the options on the "Create Additional Files" list unchecked, and select File Splitting to "By Chapter" (this will make each chapter a new track on the CD). Once done, click ok.

You are now ready to copy the DVD audio file to the hard drive, make a note of where it is going to be copies to (destination) and then click the big DVD>Hard Drive button.

It will then start reading the audio file, it may start off slow, but then get faster as it goes on.

Once done, click ok, and close DVD Decrypter.

Part 2: Burning to CD with Nero Burning ROM
Start Nero Burning ROM, it will say "New Compilation", select "Audio CD". Then under the tab "Audio CD" uncheck "Write CD TEXT on CD". then click "New".

Go to "Edit" then select "Add files".

Browse to where you selected the output files to go in DVD Decrypter, and then select all the AC3 files in there by pressing CTRL+A. Then press "Add". Once it has added them press "Finished".

b) If you add the files and they are over 80 minutes in total (many live concert DVDs etc are) then you will have to split it across 2 CDs, simply hold CTRL and select half the tracks, and add those. Then continue, once you have made the first disk (as done below) do the same again for the other half of the tracks.

and after the first half has been completed and burnt...

Go to "Edit" then select "Select All" (or just press CTRL+A again).

Then go to "Edit" and click "Properties".

Click on the "Track Properties" tab. Unless you wish for 2 second silence gaps between each track, set the "Pause" to 0 seconds.

Now click on the "Filters" tab. Check the "Normalise" box, then and take it from RMS, to "Maximum", then set the Maximum percent to 98%. This is done as many DVDs have very quiet audio compared to audio CDs, and maximisation will bring it up to a good volume. Once done, press "OK".

Once done select the burner you wish to burn with.

Then go to "Recorder" and click "Burn Compilation".

Set the write speed you want, lower will produce a better result. Make sure it is burning on "Disc-at-Once" mode. Then click "Burn".

b). You MAY get this message when you start to burn, especially if you are burning with a DVD or older CD burner. if you do just click ok. All it will mean that the 2 second silence gaps will have to be inserted between tracks. If you really don’t want this your only option is to try using another burner until you get one that doesn’t give this message.

It will then start burning, it will start by saying "Calculating [file name]" this is just it working out the volume to set each track to. It will then burn the CD to the blank disk.

One it has complete the burn click "OK" it should then have automaticly ejected your CD.

Then click done and exit Nero.

Try your CD!
Good luck, and feel free to PM/email me if you have any problems/suggestions.
Ben