What verion of Nero are you using? If Nero 8 try doing the following:
Open Nero > Create Edit > Author Edit Capture Video > Make DVD > DVD Video > Import Disk> Nero will then read your DVD and import it to your Hard Drive (Usually My Docs/Nero Vision/Imported Video.
Once imported The DVD shoud be shown in Contents, click on next Takes you to the Edit menu amend as required > Next > Preview >Burn Options (amend where necessary)> Click on Burn! Insert Blank DVD and it should create DVD.
If you are just using Nero to "clone/copy" the disk the original settings on the DVD will remain ie PC only.
Hope this helps