Holy cow, I wrote a book!
Windows Vista will not have support for really old DVD drives.
(The information below was kindly provided to me by the optical
storage driver team.)
When PC DVD drives first came out in 1998,
the drives themselves did not have support for region codes
but instead relied on (and in fact the DVD specification required)
the operating system to enforce region coding,
with the further understanding that
starting on January 1, 2000
all newly-manufactured drives
would support region coding in hardware
rather than relying on software enforcement.
For the purpose of this discussion, I will call the two types of drives
"old" (manufactured before 2000) and "new" (manufactured on or after
January 1, 2000).
It is that software enforcement that is going away.
Turns out that the enforcement of region coding in software
had its own problems:
These were among the considerations which
contributed to the decision to stop supporting these old drives.
What does this mean for you?
Almost certainly, the answer is "absolutely nothing".
First, there is no change to the way data is read from DVD drives,
so data discs will still work the same way as they do today.
Second, all new DVD drives will continue to run as they did before;
the only change is that the risk of mis-identification as an old
drive has been removed.
Only if you have an old drive will you notice anything different,
namely that encrypted/regionalized DVD movies will no longer play.
And since the average drive lifetime is only three years,
the number of such old drives that are still working is vanishingly small.
Not even the optical drive test team can manage to keep their
old drives alive that long.