I too have the same problem. I have a Liteon LTD163 DVD/CD Rom - XP Pro Desktop & in the past no problems using any of the programs you mentioned above as well as buying and installing the nVidia DVD codec for Windows Media Player. As well, only music cds & games are recognized.
As with you, after inserting a DVD into the drive it prompts me to insert a disk if I try to explore or play disk.
I upgraded the firmware on the DVD player to the most recent version & get the same results. The region is set for Region 1.
I have searched all over the internet for some answer & yet have I found any to solve this problem. All I see are people saying that they go out & buy a new DVD drive. To me that's not a solution. I have cleaned the drive & the PC has never been dropped so I know it is not damaged. I have removed the drive and reinstalled it & same thing.
If you find any solution or fix, please post it here to help myself or others in the future.
I thought it might have been the laser or optics but drive recognizes (& plays w/ no problems) cd-rom game (civilization 3) and even the most scratched music cds I have. Also recognizes all burned cds/data cds. I have played a few dvds on this computer in the past. So I know that at least it used to work. According to windows xp the driver is up to date and working properly. Compaq Presario laptop r3260 w/ combo dvd/dvd+r drive, windows xp pro sp2. DVDs will not play w/ realplayer, windows media player, or intervideo dvd player, does not show up on the my computer window, it looks like the drive is empty on this window. successfully played dvds before downloading sp2, could that be it?