Yes - there are two options available to you - providing the DVDs are your own work and do not have any copyright protection on them.
One - is to put the DVD in the DVD player tray of your PC and using "My Computer" locate all the .vob files on it - transfer these to your hard drive and change the extension from .vob to .mpg - - You should then be able to simply use any video editing programme which can edit mpeg video ( some don't do a good job with mpeg - one which does a very good job is Ulead VideoStudio) to re-edit, add music, titles etc and then burn new DVDs.
Two - you can use a programme which will import your video direct from the disc into the timeline of the programme for editing. One programme which will do that is Ulead VideoStudio. Again put the disc in your PC DVD tray - from within the programme choose "Import DVD" and follow the prompts to again have your video in the timeline for editing etc. etc. and burn a DVD.
You can learn more about VideoStudio and get a one month free trial download from here :-
http://www.ulead.co.uk/vs/runme.htm
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