If you're not burning from the original, and have all the files needed (.VOB, .IFO, and .BUP), just open up a DVD-Video compilation in Nero.
You'll be presented with two folders in the left-hand pane: AUDIO_TS and VIDEO_TS.
Copy all your files into the VIDEO_TS folder, and burn to a DVD.
It works for me when I've backed up to AUDIO_TS and VIDEO_TS on my HDD, and don't want to dig out the original disc again.
The only way that method won't work for you is if you're missing files. In which case you're out of luck unless you dig out your original and grab the missing files from that.