One of my CD's with back up data (photographs) don't work anylonger in
the CD-RW/DVD drive of my labtop. I played this CD before (the same CD
- no doubts) and were no problems. When I realize that the disc
doesn't start up automaticly, then I go to >My Computer< >CD-R< and I
have a message that: My Computer Program Is Not Responding. Moreover,
it showes that CD is blank. The other time I went to >Start< >Run< and
typed in the field: D:/setup.exe or something like that (someone told
me) and I had the dialog box on the screen that had said: CD can not
be played because the files on are in different format or the files
might be corrupted (or something like that). Amazing!!!
Did the files get corrupted by themselves? Sounds funny.
I tried to play this CD in a DVD player and still wasn't working out.
Someone told me that this could be a multisession CD which is not able
to be replayed. If it is - what a purpose to produce such a CD ?
Do all buyers know about this kind of CD ? I don't think so. Or just
with their purpose CD manufacturers don't mention anything about this,
to want rid of all multisession ones. For me that is all seems strange
anyway.
Does this mean that it  can happen to any other CD with my data,
sooner or later ? I bought all my CD's in the same, one box.

Multisession is NOT a type of disc...it defines how you burned info
onto the disc in the first place.

ie.  If I want to keep a CD in a drive and burn data to it over and
over I will make it a multisession disc.  Once I have burned all the
info I'm going to burn then I close the multisession and it becomes
readable in other drives/computers.

Anyway...you say you have played this CD already on this computer so
that would be a totally wrong path to go down.

Sounds like you have a damaged disc.  This can be scratches on the
surface which can be fixed.  Try cleaning it or a disc cleaning
machine...if that doesn't work then a data recovery company in your
area may be able to help.  If it is an old disc that wasn't well taken
care of and or of low quality then the silver in the disc could be
oxidized.  Always use the highest quality disc you can afford for
archiving (ie gold).

If you DO happen to get to read the disk, I would immediately make
another copy or two.  If it is smomething you don't want to lose, make
two copies (and test them right away).  Don't keep the two copies in
the same place - keep one offsite.

I've used a CD/DVD recovery product that will even recover quick
formatted media. You can try it for free, see it at
http://www.binarybiz.com.

Make sure that there are no scratches in the plastic media of the
cd/dvd. I've even been successful with taking my cd/dvd to another
reader. Sometimes the actual player can be bad.

Good luck!