Dear David, Thank you! Here is a sum up:

- THE ANSWER - THE ANSWER - THE ANSWER -

-So mainly the correct answer sounds like this:
You cannot disable this Excel's feature but you can change the Window's
setting according to what you want Excel to be displaying!

-How to do this?
"Control Panel" (- "Switch to Classic View") - "Regional and Language
Options" - tab "Regional Options" - "Customize..." - tab "Numbers" - And
then change the symbols according to what you want.

I want to point out that someone told me to change the cell's format to
"Text" format. This works partially, because while you can see your data as
you have written them, although when you import these data to other software
like statistical packages, then it might recognise your data as text data
(string varaible) instead of numeric data (numeric variable). So the correct
ansewer is not just to "Text" format your cells, except if that is ok with
your needs.

Thank you all & especially a great thanks to David Biddulph.