My G4 iBook will not play DVD's any more

Question

it will play CD's, but not DVD's all of the sudden. It opens DVD player and tries to look at the disc, but then says it is not a supported disc format or something like that. I've tried many DVD's, including commercially produced ones; none will play.
Used to play them just fine. I think the last thing I did before having problems was trying to install some software for a memory stick that had a secure/password authenticated area. Could I have deleted something important? This is a reconditioned Mac, so I don't have the OS discs to re-install.
Thanks very much!

Answer 1

Short of being able to try the normal and recommended paths of
restoring the software, in case something was deleted and to also
troubleshoot the hardware, most ideas may be too shallow to do
the correct job of resolving any underlying problems the computer
may exhibit since symptoms can mirror other issues.
Routine maintenance requires you repair disk permissions once
and awhile, perhaps fairly often if installing apps and updates;
since before and after each intervention is recommended by most
users with experience; the Disk Utility (see GO in Finder, note
Utility Folder) can let you run 'repair disk permissions' and also
you can try booting in SafeBoot (hold Shift key down on startup;
and then login, and then run Disk Utility's 'repair disk permissions'
followed by a normal restart. This may help clear up user issues;
but can't fix damaged or missing system parts.
Depending on what OS X version is installed in the computer,
using a bootable OS X installer disc is even a marginal choice;
since using the wrong disc can mess up the existing OS version.
You can figure out fairly close, what OS X version your iBook
shipped with by noting the hardware specs and also comparing
them against the free information from http://mactracker.ca a
download database of considerable usefulness with most Macs.
The original restore install boot disc set the computer shipped with
has the Apple Hardware Test and other options on the Installer to
include Disk Utility and the ability to do an Archive & Install, where
you can keep your user account into while the installer puts a new
system in the computer (not a first thing to do, btw.) And there are
things the correct boot installer disc allows you to do preventively.
The optical drive lens may be partially dirty; so the drive can't read
DVDs correctly. That may be remedied by using one of the cleaner
devices which could work in a slot-load optical drive. Or, there is a
chance the optical drive may be defective and require a replacement.
If the seller has any ideas on getting a boot disc (any one could look
and hope to find these original equipment parts on eBay, etc; they
should be included with the computer, however) or has a decent cost
for troubleshooting and repair - a last resort, if not a reliable company;
these avenues could be checked into first.
Not any bootable disc will work, it has to be the correct one; either one
which the system - as shipped, was installed with and came from Apple
or one which was a full retail installer disc and was newer than the Mac.
Software such as iLife was not a part of the retail OS X disc install but
may have been included with the original computer's OS X bundle.
That is to say, Tiger 10.4.0 retail won't boot an iBook G4 which shipped
with Tiger 10.4.2, etc and the Tiger retail disc won't have iLife apps in it.
Troubleshooting the optical drive and system software, along with the
rest of the computer's hardware is recommended as a first step. To
find out what is right about the computer and go from there... And to
do that, certain basic tools such as the OS X installer is recommended.
Or take the computer to a shop where they have an authorized repair
station set up and a trained technician who knows your product well,
is the correct and non-assuming way to work on resolving this issue.
Do you have more specific machine information to identify which iBook
G4 you have? There is info in System Profiler, and also on the Mac's
case; the latter would show the as-shipped hardware configuration
while the System Profiler (see About this Mac, under Blue apple menu)
may show any changes or upgrades in hardware, as well as OS version
and applications installed in the system.
It may be possible to download just the DVD Player from Apple Support;
it would have to be the correct one for whatever OS X version you have,
or if you had a retail OS X installer plus got the Pacifist utility, you could
scavenge the DVD Player from the installer disc and only install it.
Good luck & happy computing!
edited to add more words.