I'm launching the following command in DOS :
php c:\composer.phar create-project C:\Symfony C:\Users\Jerome\git\XX\XX
Invalid argument exception, could not find package C:\Symfony but all
the files are there.
The command you need is:
php composer.phar create-project symfony/framework-standard-edition C:\Users\Jerome\git\XX\XX 2.1.2
symfony/framework-standard-edition
is not a path, it is a package name