MichaelV26 said:
As stated above, I am using Windows XP Pro SP2. I hope I chose the RIGHT
Category for my question. I am NEW at this, so bear with me.
I am stuck with a question that I hope someone can give me an answer that is
detail and perhaps a free tool if someone has it. The question is BEFORE
installation any CD or DVD, I want to be sure the CD or DVD has NO errors of
any kind, so that I am confident that I will have installed a excellent
operating system with NO errors that will caused my system NOT to work the
way it should work. This TOOL must be able to detect errors in operating
system,etc....
The SECOND question is about cleaning the DVD or CD. I am using MEMOREX
OPTIFIX PRO, which I hope someone is familiar with it. Do you think this is
SAFE to clean operating systems or any MAIN DVD or CD?
Optical devices use Reed Solomon error correction codes, to make
the reading process more robust. The Reed Solomon code, allows
errors to be corrected. The code is interleaved, and multidimensional,
with the result that it takes large physical defects (scratches),
to cause significant problems.
http://en.wikipedia.org/wiki/Reed_Solomon
The first problem with your question, is whether it is possible for
a person to read "raw" data from a CD or DVD. The thing is, all
that hardware in the controller is at work, and it tries to
correct the errors before forwarding the data to the user. So
any tools you might use, aren't really looking at the "raw" optical
signal.
There are websites that review optical drives, and they use
tools like Kprobe to evaluate media or burns. If you look at
the results here, you can see an "error" curve. Now, even though
the curve shows errors present, in all probability, the CD or DVD
these were made from, is perfectly readable. No CRC error or
error indication of that sort, might be seen at the user level.
But the shape and amplitude seen in these plots, gives the
user some idea of the quality of the burn. If you see
thousands of errors for example, you might expect problems
a few months from now, if the dye starts to degrade.
http://www.cdfreaks.com/reviews/NEC-ND-3520A---Modified-vs_-stock-firmware/KProbe-explained.html
At one time, I had a Liteon brand drive, so I could use Kprobe with
it. It was interesting, to buy different brands of media from a
local big box computer store, and do test burns on the Liteon.
Some of the media give dreadful results, with thousands of
errors showing up in the scan. The media was so bad, it
caused the burner to "freeze" attempting to re-read the
bad bits. So you could tell there was a significant problem
with an optical disc.
But for other brands of drives, you may not have a tool like Kprobe
to use. Or, the error flags Kprobe is using, may not be available
for whatever reason. That means it isn't a given, that if you
pick an optical drive, that there will be low level tools waiting
for you, to dial in the device (i.e. match a good brand of media
with the new drive).
Some people, might use two drives. They'd keep a Liteon around,
just so they could use Kprobe. They'd use another drive, to burn
hundreds of disks. It there was any concern with the burn quality,
inserting the disk in the Liteon and running Kprobe might provide
the necessary feedback, on how well the new burner is working. But
drives can differ, in their opinion about a disc, and what one
drive sees as "defective", might read perfectly well in a different
brand or model number of drive.
As for cleaning, I find the notion of cleaning everything, to be
risky. For example, say there was an abrasive grit on the surface
of the media, you used some kind of "cleaning kit", and left
hairline scratches all over the place. Media works best, if you
don't leave finger prints all over it. Handled with some amount
of care, there is no reason for contaminants to be all over the
place. (I keep all my media in jewel boxes, so there isn't a reason
to expect contamination.) I don't own a cleaning kit, and don't plan
to start anytime soon.
As for an "end-user" style test, that could be achieved by reading
the entire disk, and capturing the data. For example, there are
utilities that will read a piece of optical media, and offer to
make an ISO9660 file from it. You could use a checksum tool
(using MD5 or SHA1 algorithm), to compute a checksum over the
entire ISO9660 file that was generated. If you compare your
MD5 to another person's MD5, and they agree, then you know
the two disks are highly likely to be identical. Does anyone
publish a list of MD5SUMs for Microsoft install CDs ? That,
I don't know. But that is how you go about, succinctly,
comparing two discs to one another - convert to ISO9660,
checksum, and compare the checksums.
At least some of the Linux distros you can download, provide
an MD5SUM on the download page, so you can check them later.
If I can remember to do it, I copy the MD5SUM text string,
to the label on the jewel box, so if there is trouble later,
I can verify the thing with some amount of work.
Paul
