I've been struggling with this problem for some time now. Not exactly sure what I did to screw it up, but....I have a Plextor 760A DVD drive. Used to play and burn everything fine, have tons of data DVDs. But for the past several months my drive hasn't been able to even recognize ANY data DVDs (of which DVDs I know are good copies and have worked fine in the past). It plays most video DVDs, but some (I guess cheaper quality DVDs) won't play or recognize. As well it won't recognize any regular data CDs, with the exception of the Windows XP CD.
I have tried different hardware configurations, different cables, and even installed a fresh version of WinXP....exact same problem remains. When I use the drive to boot from, the WinXP CD works fine, but the Vista DVD won't work at all. I guess that pretty much eliminates it being a software problem. I've had the drive for probably a year and a 1/2, and hasn't been abused much. Could the lens maybe just be dirty or something simple like that? What kinds of things could I do to test the drive to make sure it's still good, from a hardware standpoint?