Wow... noone really listened to you it seems. First, the fundamental breakdown:
1. Extract the correct scenes from the existing DVDs
2. Convert then compile them into a SINGLE movie format (using many DVD files) to put on a DVD
3. Burn said DVD.
Per #2... a DVD .. think of it as not dragging and dropping a bunch of videos... it needs to take all them and convert them into one giant show. when you convert 10 videos or whatever for DVD... it combines them, then splits them up for the sake of filesizes... into something you wouldn't recognize.
Ripping them off the DVD is easy. There's a boatload of free/pirated software out there.... however, most aren't as easy as saying , give me track 3. You usually will be working with a "time/scene based" editor, where you pick the start and stop times from which to pull. Given you want particular scenes, and keeping in mind my point above... the scenes don't exists like "tracks" of an audio CD...
The software, then needs to convert or do something with that scene..... convert it to AVI or MPG or keep in DVD formats (VOB) to store .. to pull again.
Then, pending your (next) software, you might be able to just drag/drop or import those video files into a master disc... many new computers come with software to do just that thing. Some may want to re-convert everything, regardless.. which is a good 20-45 minutes. But they'll usually allow to create movies with creating menus, titles, and so forth.
There's more advanced and intermediate program sthat'll allow to have more control, but takes a bit more deft. For me:
AVS Converter... converts anything and everything into anything and everything. Comes with burning capabilities... but I prefer to stop after.
I doubt HIGHLY there is one software program that will do that, much less with copyright protected DVDs.
Nero, as mentioned, I highly recommend as well. and keep in mind... plan on wasting a shitload of blank dvds... not only trying to figure it out, but figuring out which DVDs work with your burner.... check it out on the net... you'll see discussion around "coaster ratios". I'm sure many LPSGers have enough "coasters" and have done rather artistic version with "coasters". I've had a few successful burns, but the audio is off, or it wont' play in my bedroom, or whatever...
... at least blank DVDs are pennies these days. Even the double layers might drop below a $1 soon.