Data that has been burnt onto a DVD-R disc is permanently stored on that disc. Due to its unique characteristics (specifically the disc's dye), data cannot be erased on a computer, as with a DVD-RW disc. However, if you need data removed from a DVD-R disc, the only way to complete this task is to destroy the disc. This can be done by scratching the disc until it is no longer readable.
Take a screwdriver, or other similar sharp object, and scratch the top and bottom of the DVD-R thoroughly.
Test that the data has been erased by inserting into a DVD player or a DVD drive in a computer. If the disc plays, eject and scratch the disc again.
Continue to test in a DVD player or computer DVD drive until the disc is no longer playable. Discard the now useless disc.
To record data on a DVD disc that can be erased later, be sure to use a DVD-RW disc instead of a DVD-R disc.
Be careful when using a screwdriver or other sharp objects, as the possibility of slipping on the disc and stabbing yourself exists.