Verified answer

Not erasable. Once the disc is full you cannot add more data to it. More info on this and other optical disc formats at the source below.

Once you record on a dvd-r disc, you can not erase it. Use a dvd-rw disc if you want to re-use it and it can be erased several times

You can only erase(format) DVD-RW /DVD+RW discs.To format these discs there's a free software called " BurnAware.

How to format Re-Writable DVD's using BurnAware@

http://www.youtube.com/watch?v=-KnkfBv-0tY

DVD-R and DVD+R are "write-once" media. You can't erase them. For that you need DVD-RW or DVD+RW media.