[Foreigner]

Код:

$files = Get-ChildItem C:\Directory -File -Recurse
$zeroes = ($files.Count).ToString().Length
for ($i = 0; $i -lt $files.Count; $i++)
{
    $New = "{0:d$zeroes}.{1}" -f ($i + 1),$files[$i].Name
    Rename-Item $files[$i] $New
}