First, thanks for the recommendation Roadrunner... I thought that might be it since, according to the information on the Media Player Classic page on Wikipedia it says,
"Media Player Classic is capable of VCD, SVCD, and DVD playback without installation of additional software or codecs. MPC has built-in codecs for MPEG-2 video with support for subtitles and codecs for LPCM, MP2, 3GP, AC3, and DTS audio."
So I thought that since it has its own built-in codecs that might solve the problem, but it didn't. Since Media Player Classic does not actually install, and it just runs from the folder that the zipped file is extracted to, then I don't see how that would affect the DVD drive itself, right?
And thanks to jumanji and firebird for your input as well.
The Windows Media Player that is on this computer is version 12.0.7601.17514 dated 11/14/2010. I think I upgraded it once since I installed Windows 7 in October of 2010. But apparently that doesn't have anything to do with this problem because Media Player Classic HC doesn't see the same DVDs that WMP won't see.
Let me clarify, with the DVDs that won't play, the DVD drive does not show that there is any disk in the drive when I look at the Computer window that shows my drives... it just appears that the DVD drive is empty, whereas when there is a DVD in the drive that will play, it shows the disk and the name of the disk in the E drive.
The problem is that the DVD/CD drive is just not seeing some of these DVDs, and as I said, many of the DVDs that it will not see are from the U.S. market, and even some from the same distributor will play and others from that same distributor will not. In addition, most DVDs from Japan will play and some will not. At this point after testing about 50 or so DVDs, the ones from Japan have a better play ratio then the ones from the U.S... but a few of the DVDs from Japan will not play.
Could that have anything to do with the fact that this 2006 computer's DVD drive is a Japanese model? Again, it is a SAMSUNG HD161HJ SCSI DVD/CD Disk Drive
I thought that possibly more codecs would make a DVD drive see more types of DVDs, but I think I understand now that isn't the case. Codecs make a video player play or convert more types of video and video editing apps deal with more types of video formats, but it has nothing to do with what a DVD/CD drive will see, right?
I edit and create some videos in Adobe Premiere, so I have at least a vague understanding of codecs and I've installed some on this computer... but I don't believe that has anything to do with this problem.
Is it possible that a newer software driver for my internal SAMSUNG HD161HJ SCSI DVD/CD Disk Drive would make it see more types of DVDs? Maybe I was wrong with my previous assumption that the driver won't make a difference.
Or is it possible to "set" the region for the DVD drive, as firebird indicated? How does one go about doing that?... and would that be likely to make it so it wouldn't play some of the DVDs that it will play now?