I had the same problem you do; I purchased a NEC DVD burner and could play CDs, but not DVDs, even though I had installed the basic Nero software that came with the drive. I contacted NEC and was told that the DVD Codec I needed was available from (intervideo) WinDVD or other such sources. I installedd the 30 day trial version and the player worked as it should. I immediately purchased the full version once I was confidant that my issue was resolved. You can go to Intervideo's site and download the trial version to see if that helps.
I have a Samsung TS-H552 DVD+RW. A website for the SPECS is http://www.overclockersclub.com/reviews/samsung_ts-h552_dvd_burner.php
Now my problem is that the burner will allow me to read/write to CD's, but wont read/write DVD's. Perhaps someone could help me?
My pc specs are as follows:
P3 1.31 GHZ
NvIDIA GEFORCE 4 64MB
Windows XP PRO
768 MB SDRAM
More than enough to support the drive, i jsut need some help...anyone out there?!