I'm not sure about the programs you are using. Dose the program your using have the option to burn a DVD to another DVD? If not, Nero6 Dose, Nero7 is out now, I'm sure it has the same option as Nero6 (Burn at once).
To back up your DVDs you need a program to get rid of that pesky copy protection, You can use "Any DVD"
If you want to make a couple copies of the same DVD you can use "Clone DVD or Nero6/7" You down load the DVD to you hard drive, Then you Just put a blank DVD in your DVD drive and hit copy, when that one is done, pop another blank DVD in the DVD drive and hit copy.....
In both Nero and Clone DVD you have the options to Copy the DVD "as is" or you can modify it to NOT have menus, DTS, 5.1, Subtitles or whatever you don't want. If you get rid of the menus, The DVD will automatically play when you put it in your DVD player (Very Nice
Most movies on DVD are DL DVDs (dual layer) They are 8GBs. The regular blank DVDs are only 4.7GBs so if you want to burn a DL DVD(8GB) to a regular DVD (4.7GB) you have to compress it, witch will lower the quality, or you can take off the menus etc...
If you want to buy a new DVD burner, Make sure its a DL burner so when blank DL DVDs become cheaper you can use them, last time I checked a couple months ago blank DL DVDs where 15 bucks each
Clone DVD and Any DVD free Trials http://www.slysoft.com/en/
Nero7 free Trial http://ww2.nero.com/enu/index.html