Go to bios and change the dvd drive settings to DMA mode. After that go to IDE/ATAPI controller under device manager and change the settings to DMA. restart system and give it a try again
OR
After changing/confirming that the dvd drive settings on the bios is on DMA, install this:
http://tinyurl.com/5w7yqt
and restart.
See if the dvd is getting burnt. If not try on 8x. If that doesnt work try using cd burner xp. Let us know how it goes from here.