In article ,
legg wrote:
On Mon, 3 Aug 2020 08:29:34 -0700 (PDT), "
wrote:

You need to understand that the recording medium on an R or RW DVD and on a commercially printed DVD are entirely different. The one is a dye that is 'burnt' by the
laser, the other is quite literally stamped. Over time, the dye will deteriorate even by playing - which is via the laser at a lower power than when burning - and become
less contrasting. At which point it becomes more difficult for the laser to read it. Not true of a stamped DVD. I have always taken the position that a DVD R or RW is a
volatile storage medium, not for the ages, as it is chemical in nature.

Peter Wieck
Melrose Park, PA

I realize that these DVD-R media have a half-life,
however - being unable to detect a blank DVD-R or
DVD-R from multiple vendors probably indicates that
the issue lies outside the media itself.

Don't you agree?

Strongly suspect a Windows issue - though how it could
surface in both a W2K and a W7 system, simultaneously,
is begging belief. I'm concentrating on the W7 system
as priority, as the internet-isolated W2K system has
limited and specific duties that only seldom requires
reading from DVD data.

I'd suggest this, to trouble-shoot: download a "live Linux"
distribution (there are quite a few), write the .iso file to a USB
stick, and boot it. All of them should be able to read a burned DVD
and (usually) mount the filesystem on it. Most of them come with (or
have the download capability to fetch) DVD-burning software such as
Brasero.

This would let you test the same drives (with their firmware) and the
same discs, without using any Windows software at all, thus
eliminating this one factor completely. Whether you can read the
discs or not, it'll give you a good idea as to whether Windows issues
are involved.

You might be running into this problem for any of several reasons:

- Dye deterioration on the DVD discs. Some dye types, and some brands
are less stable than others. Storage conditions (temperature,
humidity, and exposure to light) may matter.

- Failing laser(s) in the DVD drives.

- Dirty (or smoke-coated) lenses in the optical systems. If anyone
smokes tobacco or other herbs around those computers, this could be
a real problem... tobacco "tar" coating the lenses is bad juju for
the system.

All of these problems would affect "burned" DVDs more than pressed
ones, as the relative reflectivity differences between "1" and "0"
bits is lower, and the signal "seen" by the laser/photodiode system is
weaker. Back in the Olde Days, many first-generation CD
players/drives had trouble reading CD-R discs, and many couldn't read
CD-RW, for this same reason.