How do you test burn? I say this because I have a DVD+R 8.5 gigs, and if I mess up (which already happened once), I will lose the DVD+R, which cost me 13 euros.
First of all I wouldn't use Nero to burn a +R DL disk. ImgBurn and DVD Decrypter are both better DL disk burners imho. Second, test burning won't ensure that the actual burn will be successful, only that the burn is possible. Third, for successful DL burning, the burner firmware needs to be up to date. Lastly, one needs to use decent quality DL media. Verbatim seems most compatible with most burners and also is of the highest quality.
Since you had an unsuccessful burn previously, something is likely amiss with the firmware, etc.
If you're backing up a disk you own, you can just use DVD Decrypter to both read and write as long as the disk doesn't have strong copy protection. If it does, you'll need AnyDVD running in the background.
In DVD Decrypter:
Set the mode to ISO Read and rip the disk to your hard disk.
Insert a blank disk.
Set the mode to ISO Write and select the mds file that is a companion to the ripped dvd iso image file. It contains the layer break info.
Set the burn speed to 2.4X and burn.
If you don't have AnyDVD, then rip with Ripit4me, output an ISO image file in the Shrink portion and burn with ImgBurn following these guides:
You can test burn a DVD by selecting the image recorder instead of your DVD burner. It will burn an image to the hard drive. You later burn the image to a DVD if you want using Nero Burning ROM.
Some folks have problems with DL burning in Nero and some don't. I have burned several and had no problems.
