*seraching for code that finds the computer ID

Hi all !
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every computer has an ID number that is unique to its board.
I've heard that someone found how to "read" this number from the
computer,
and by this he can identify on which computer does the program run on.

I am not a pascal programer myself so i'm sorry for the non-proffesional
writing,
but if anyone knows how to do this or what's the code or know where can
I find it then please send email to me :

mu...@netvision.net.il

           thanks very much !!!!!!!!!!!!!!!!!!!!