How to know if a clean XP install is good?

  • Thread starter Thread starter shanex
  • Start date Start date
S

shanex

Hi all,

We all know that CD/DVD drives, depending on their quality, can often
mis-read occasionally, especially if the cd in question had surface marks
say.
So if I install XP from a cd which is not in 100% perfect condition, and the
install completes without issue, can I really be sure that all is well? If my
drive mis-read a few bits during the installation, how would I know? Would
the XP installer be guaranteed to detect and flag such a fault? Or would it
just proceed, allowing incorrect data into the install?

Is there a way, post install, to determine the "goodness" of the installation?

Many thanks for any thoughts!
 
When XP installs, it does a check on the files. If it installed correctly,
then all is well.
 
Hi Dustin,

Thanks for that. But how does this work? A file gets copied incorrectly from
cd say, during install, because cd is bad, or drive is bad. If checksums are
calculated before and after copy, presumably the 2 checksums could be wrong
(but identical)...
Unless checksums are stored on the cd seperately, and after copy you check
copied checksum against checksum on cd?
Or how does it work?

Thanks!
 
Let me describe my actual scenario:

I have a good cd drive (plextor premium), and about a year ago I used it to
create an iso image (plextor have their own version of iso called .pxi file)
of my xp cd, as a backup, to protect against cd damage. In fact I created 2
pxi images of the cd, binary compared them and they were identical. Call
these 1.pxi and 2.pxi say.

Yesterday, one year later, I did the same process. Same cd, same drive,
same pxi creation tool. I created 3.pxi and 4.pxi and again they were binary
identical.
However if I binary compare 1.pxi and 3.pxi there are differences.

My conclusions:

1) 1.pxi = 2.pxi and 3.pxi = 4.pxi implies drive is ok
2) 1.pxi not equal to 3.pxi implies cd is not ok. And indeed, there are some
light marks on the cd which were not there when it was new.

However I used this cd to install xp successfully, also yesterday. So my
dilemma is: I know (almost 100%) that the cd has changed over time due to
some very light marking, and yet I get no complaint from the xp installer if
I use this cd to install xp.

That's my real question !
 
shanex said:
Let me describe my actual scenario:

I have a good cd drive (plextor premium), and about a year ago I used
it to create an iso image (plextor have their own version of iso
called .pxi file) of my xp cd, as a backup, to protect against cd
damage. In fact I created 2 pxi images of the cd, binary compared
them and they were identical. Call these 1.pxi and 2.pxi say.

Yesterday, one year later, I did the same process. Same cd, same
drive, same pxi creation tool. I created 3.pxi and 4.pxi and again
they were binary identical.
However if I binary compare 1.pxi and 3.pxi there are differences.

My conclusions:

1) 1.pxi = 2.pxi and 3.pxi = 4.pxi implies drive is ok
2) 1.pxi not equal to 3.pxi implies cd is not ok. And indeed, there
are some light marks on the cd which were not there when it was new.
Click to expand...

Duh! The creation dates differ.

However I used this cd to install xp successfully, also yesterday. So
my dilemma is: I know (almost 100%) that the cd has changed over time
due to some very light marking, and yet I get no complaint from the
xp installer if I use this cd to install xp.

That's my real question !
Click to expand...

Sort of related:

The process used to create CDs on your home computer varies drastically from
the method used to create CDs commercially.

When Microsoft finishes development of a software package, including XP,
they RTM. That's Release to MANUFACTURING, not "duplication." Commercial CD
making involves "pressing" an image on an injection molding device, like
chiseling a name on a granite tombstone. A CD-R uses a dye that simply
changes color when subjected to a particular frequency of light, like
printing the Sunday comics.

The durability of a "pressed" CD is virtually infinite in that it is a
physical construct. A CD-R, not nearly as long (about five years). CD-Rs
degrade over time and use, eventually becoming unreadable.
 
HeyBub,

I didn't know that creation dates are stored inside pxi files. Are you sure
of this?

I'm aware on the different processes btwn pressed cds and cdrs.

My question really boils down to: if an xp install cd has a *known* error on
it (even just 1 bit), and your cd drive doesn't flag it, will the
installation process inform you of this error bit, or not. I suspect not. I
can't see how every bit of the install is verified after installation. But I
look forward to the counter argument.

Thanks.
 
Hi all,
We all know that CD/DVD drives, depending on their quality, can often
mis-read occasionally, especially if the cd in question had surface
marks say.
So if I install XP from a cd which is not in 100% perfect condition,
and the install completes without issue, can I really be sure that
all is well? If my drive mis-read a few bits during the installation,
how would I know? Would the XP installer be guaranteed to detect and
flag such a fault? Or would it just proceed, allowing incorrect data
into the install?

Is there a way, post install, to determine the "goodness" of the
installation?

Many thanks for any thoughts!
Click to expand...

You could run sfc right after the install completes. That checks all
the programs are there and working if you're in doubt.

A clean install without errors though is higly likely to be OK; it has a
lot of error checking built right into it.
--

Regards,

Twayne

OO0 is a GREAT MS Office replacement
www.openoffice.org

Please respond to the newsgroup, not to
my e-mail, so that all may benefit. I do not
always respond to newsgroup e-mails.
 
shanex said:
HeyBub,

I didn't know that creation dates are stored inside pxi files. Are you
sure
of this?

I'm aware on the different processes btwn pressed cds and cdrs.

My question really boils down to: if an xp install cd has a *known* error
on
it (even just 1 bit), and your cd drive doesn't flag it, will the
installation process inform you of this error bit, or not. I suspect not.
I
can't see how every bit of the install is verified after installation. But
I
look forward to the counter argument.

Thanks.
Click to expand...

The installer checks for any errors (CRC or cyclic redundancy check) which
will ensure that all the correct data has been sent to the computer. If
there is any type of read error or the count in the CRC is incorrect the
installation will fail..;
 
My conclusions:
1) 1.pxi = 2.pxi and 3.pxi = 4.pxi implies drive is ok
2) 1.pxi not equal to 3.pxi implies cd is not ok. And indeed, there are some
light marks on the cd which were not there when it was new.
Click to expand...

Here's my shot in the dark.
What other info is in the .pxi files, besides the .iso data read from
the CD?
If were to contain sommething like say the date of creation, then
1.pxi, and 2.pxi created the same day would indeed be binary equal,
and 3.pxi and 4.pxi created the same day again, binary equal, but
different from 1 or 2.pxi

Maybe you need to make a "real" iso image of your disk.
http://isorecorder.alexfeinman.com/isorecorder.htm



However I used this cd to install xp successfully, also yesterday. So my
dilemma is: I know (almost 100%) that the cd has changed over time due to
some very light marking, and yet I get no complaint from the xp installer if
I use this cd to install xp.

That's my real question !
Click to expand...

As the data is being read from the cd it is checked with a CRC (Cyclic
Redundancy Check) code. It's like knowing how many 1's and 0's there
should be. If the count's wrong, then depending on how many errors
there are, they can be fixed as they are read. If there's too many to
fix, then the faulty block is read again. It's VERY clever how it
works.

Good luck.
 
Hmmm, I'm not convinced. I just ran the same pxi extraction now as I did
yesterday. Binary identical. So unless it only stores the month and year ...!
 
shanex said:
Hi all,

We all know that CD/DVD drives, depending on their quality, can often
mis-read occasionally, especially if the cd in question had surface marks
say.
So if I install XP from a cd which is not in 100% perfect condition, and
the
install completes without issue, can I really be sure that all is well? If
my
drive mis-read a few bits during the installation, how would I know? Would
the XP installer be guaranteed to detect and flag such a fault? Or would
it
just proceed, allowing incorrect data into the install?

Is there a way, post install, to determine the "goodness" of the
installation?
Click to expand...

The data structure on a CD or DVD has inbuilt error detection and
correction. Most people are singularly unaware of how many read errors
actually occur when reading CDs or DVDs because this all happens
transparently. The error detection is able to detect the error and (if it
is not too serious) correct it. If it can't be corrected, an error message
will tell you.

If your XP installation has proceeded to its conclusion, then no
unrecoverable errors have occured.
 
M.I.5¾ said:
The data structure on a CD or DVD has inbuilt error detection and
correction. Most people are singularly unaware of how many read errors
actually occur when reading CDs or DVDs because this all happens
transparently. The error detection is able to detect the error and (if it
is not too serious) correct it. If it can't be corrected, an error
message will tell you.

If your XP installation has proceeded to its conclusion, then no
unrecoverable errors have occured.
Click to expand...

Yes. If setup can't read a file from the disk during install you will get an
error message to that effect - (not that that means the disk is FUBAR).

I doubt any OS install would let you continue without a critical component.
 
Hi,

Copy your #1 and also your #3 to your hard drive. Open them both in
seperate file explorers and see where they differ, folder by folder.

---==X={}=X==---

Jim Self

AVIATION ANIMATION, the internet's largest depository.
http://avanimation.avsupport.com

Your only internet source for spiral staircase plans.
http://jself.com/stair/Stair.htm

Experimental Aircraft Association #140897
EAA Technical Counselor #4562
 
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