Are you running 2 drives?
eg. DVD-Rom + CD-Writer\ROM??

But You can get your CD-Writer\Rom to work properly, but your dvd-rom runs as a standard cd-rom drive and its not picking up DVD's?

Heres The FIX:
Navigate to your device manager located in you system; in your control panel...Once there, click on "ATA/ATAPI controllers" open: "Secondary IDE channel" click the "Advanced Settings" tab: If your DVD-ROM is the master and your CD-Writer\Rom is a slave change the device 0: Transfer Mode to "PI0 Mode" in the drop down menu... or if your CD-Writer\Rom is master and your DVD-ROM is slave (which is really rare) change the device 1:transfer Mode to "PI0 Mode"in the drop down menu... Then restart your computer even if it doesn't ask you to!

once restarted... Test!! and have fun... :)

PEAC3 .:.: Tw3aKm3 :.:.