Try using the following:
$TheFile = basename($File);
header( "Content-Type: application/octet-stream");
header( "Content-Length: ".filesize($File));
header( "Content-Disposition: attachment; filename=".$TheFile."");
readfile($File);
This code sends any documents to the browser telling it that this file must be downloaded. You can even try with .pdf, images and almost any kind of file.
Hope it helps
fLIPIS