A friend's Samsung desktop internal combo drive (CD burner, DVD player) was 
hung while playing a DVD+RW disk via Cyberlink PowerDVD v4.  Sorry I
do not have the Samsung model number.  I could not end the powerdvd
process (it was not responding) so I had to do a hard shutdown of
Windows XP.

The drive can still read CDs and burn CD-R.
The drive can recognize a commercial DVD but the playback is extremely
stuttery (!) and the audio is distorted.  It seems almost like the
drive is on a skip-ahead mode.

I think his drive is now shot. I'm sorry I powered down too.

Q1) Do combo drives have two lasers, one for CDs and another for DVDS?

Q2) What would explain the fact that it can still function as CD
burner but DVD is no good?

We are 99% sure it is shot and so he will get a new combo drive but it
would be nice to the why anyway.

Hi grt...

There's only one laser in the drive, but before you toss the 
unit, consider the very real possibility that, in performing 
the hard shutdown of Windows, you caused damage to one of the
files in the Cyberlink PowerDVD v4 software, or, worse, one
of the Windows files which supports the DVD drive functions.

You might try uninstalling and reinstalling Cyberlink PowerDVD,
and see if that resolves the glitching. And certainly, before
investing in a new unit, borrow one from someone you know, and
temporarily install that one and test it with the system. That
will tell you for certain if it's the unit or a software 
problem. You could also use alternate DVD player software, if
you have that available, and see if that makes a difference.

If a reinstall of PowerDVD and a test of a borrowed unit still
leaves you with a problem, then you might need to use Windows
System File Checker to restore any damaged Windows files, but
hopefully, and likely, it won't come to that.

Also, when you're testing the DVD function, are you using a
different DVD than the one you were using when you shut down
the PC? It might be that that particular DVD is damaged, and
another will work.

Next time you want to end a program that's not responding, 
press and hold Ctrl, Alt & Delete and open the Task Manager.
You can usually end a process from there, even when it's not
responding to normal cues.

I think that about covers all the bases for the situation as
I understand it.

Let me know where this takes you, and what else you might need.

sublime1-ga