code listp to determine wich os I'm running on

[Renato]

Hi,
I'm looking for some code to insert in my .emacs to determine wich s.o 
I'm running.
've foud this code:
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;; check OS type (cond((string-equalsystem-type"windows-nt") ; Microsoft 
Windows (progn(message"Microsoft Windows") ) ) 
((string-equalsystem-type"darwin") ; Mac OS X (progn(message"Mac OS X") 
) ) ((string-equalsystem-type"gnu/linux") ; linux (progn(message"Linux") 
) ) )
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but I do't know lisp (I will learn it, of course...but not now...)
I've understand that if I'm running Linux if I press F1-e, in the buffer 
I can read "linux".

But What do I have to do to set a particular path (setq load-path... to 
start from if I click
for my C-x f in emacs on linux or win?

I mean wich variable do I have to check? and how do I build the if 
statement?

TIA

Renato