I\'m using gvim on Windows.
In my _vimrc I\'ve added:
set shell=powershell.exe
set shellcmdflag=-c
set shellpipe=>
set shellredir=>
function!
None of the answers on this page were working for me until I found this hint from https://github.com/dougireton/mirror_pond/blob/master/vimrc - set shellxquote= [space character] was the missing piece.
if has("win32") || has("gui_win32")
if executable("PowerShell")
" Set PowerShell as the shell for running external ! commands
" http://stackoverflow.com/questions/7605917/system-with-powershell-in-vim
set shell=PowerShell
set shellcmdflag=-ExecutionPolicy\ RemoteSigned\ -Command
set shellquote=\"
" shellxquote must be a literal space character.
set shellxquote=
endif
endif