Isso deve ser o que você precisa:
$Process = new-Object System.Diagnostics.Process
$Process.StartInfo.UserName="Administrator"
$Process.StartInfo.Password=$Credential.Password
$Process.StartInfo.Domain="$Computer"
$Process.StartInfo.WindowStyle="Hidden"
$Process.StartInfo.FileName="cmd.exe"
$Process.StartInfo.Arguments="$localArgs"
$Process.Start()