The _vimrc file in this directory
is for use with Vim under Windows.
Copy it and place it in the root
directory of the account you use
to log in to your Windows account.
It must have that exact name (_vimrc)
and be in that location for Vim
to find and use it.

If you want to use the file under Linux
or on the Mac (which is Unix under the
hood), you must use the file dot.vimrc,
not the _vimrc used for Windows. But you
must also change the name of the file to
be .vimrc (not dot.vimrc), and once again,
on Linux or the Mac, the file must be placed
in your home directory so that vim can find it.