I have a Plextor PX-740A giving me trouble. I am able to read CD's, but unable to read dvd's. I should also say that I recently had to replace my mother board. When I started up my new motherboard, windows xp SP3 did take a while to get up to par with all of the device changes from a new motherboard. I've been having problems with my CD/dvd drives since. I have deleted the upper and lower filters from the registry, updated the firmware for both of my drives (Sony DRU-810A is my other drive). I now have my sony drive rockin and rollin, but I can't get my Plextor to read DVD's. I ran the CD diagnostic program in ITunes and this was the results for the Plextor drive.
Microsoft Windows XP Professional Service Pack 3 (Build 2600)
BIOSTAR Group T41 HD
Apple Application Support 1.1.0
iPod Updater Library 9.0d11
CD Driver 184.108.40.206
CD Driver DLL 220.127.116.11
Apple Mobile Device 18.104.22.168
Apple Mobile Device Driver 22.214.171.124
Bonjour 126.96.36.199 (118.5)
iTunes Serial Number FF527504B84D54B1
Current user is an administrator.
The current local date and time is 2010-01-12 21:47:18.
iTunes is not running in safe mode.
I assume you removed the AnyDVD and GEARAspi filters?
Run an advanced diagnostic utility such as Opti Drive Control. Insert different DVDs (pressed/burned) and run the transfer rate test (benchmark).
If the discs are not detected then your DVD laser may have died. Unfortunately there's nothing you can do about that.