In Nero you should use the DVD DATA option. You can not burn an audio DVD with the Nero product.
In Nero 5.5; change the supported media option by using the drop down menu above the burn formats (You will find this option the "New Compilation" window). This menu will probably only display DVD and CD. Select DVD. Next select "DVD-ROM(ISO)" icon right below the media option . Also, change the "Multisession" option to "No Multisession". This will prevent you or someone else from screwing up your DVD.
In Nero 6; you can launch the Nero StartSmart, select the DVD tab in the upper right hard corner, move your mouse over the "DATA" format icon and click on "Make Data Disc".
Note: If you using Nero Express, uncheck the "Allow files to be added later (multisession disc)" and check the "Verify data on disc after buring".