Hp uable to read data dvd;s

Question

Have a HP Pavillion 9426f, running Vista 64 bit.
Have three other computers all running Windowns Xp, have created data discs in all (total about 25).
Discs were created using dla and then made compatable.
In addition to the computers at home, in my wifes office, computers there can read discs also.
Hp cannot read the discs.
1. The computer knows the disc is there, it gives the kind of disc, and the total used.
2. The DVD burning software can make a copy of the disc, if when played on a xp machine
works perfectly ( the copy)
3. Computer can play, recognize all other discs, and can burn ok.
4. Today (12/08) purchased an external dvd writer and hooked it to the computer.
It will be returned,same problem, So it is not the dvd writers fault
Have contacted HP support, technician spent about two hours on the phone, nothing.
Any help or suggestions appreciated.

Answer 1

Sorry to not have included that.
If I burn an entire disc at one time on another computer, using something
like Roxio or Nero ( have both)or Cyberlink. Computer can read the disc.
Appears only the "burned" dla ones cannot be read.
Again, not dvd writer, not software, not drivers, technician when working on computer
took it over and installed "readers" such as UDF.
Believe you might be right regarding dla, but it would I think be generally Vista vs  DLA.
Not the computer.
As the technician and I agreed, since the dvd can write a dvd ok, and read other formatted disc,
HP was not strictly to blame.
Reason for posting here is that sooner or later someone else will have the same problem.
Also, as I told him, am fortunate enough to have another computer that will read all the discs.
If this was a replacement.........