Put a new DVD-R in the drive. Launch Nero and write in ISO mode. Select START MULTISESSION. Burn data to DVD. Check to see if you can read this disc with your DVD ROM.
To add more data to the DVD-R, put the DVD in the DVD burner and launch Nero. Now use ISO mode, but you want to select CONTINUE MULTISESSION. Add and burn data to the DVD. Again, verify that you can read using the DVD ROM.