Windows 7 and Vista for that matter, does not activate the Briefcase feature by default. The Briefcase was a utility to let users sync files between two computers. But it is not much used since Vista.
To create a new Briefcase right click on a blank area on the desktop or in a folder > New > Briefcase.
If you wish to remove Briefcase from the list of New items, open regedit and navigate to the following registry key:
HKEY_CLASSES_ROOT\Briefcase
Delete the ShellNew sub-key away with all its values.

This will make Briefcase disappear from “New” item list.
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