<?php
$file=array();
$file[]='susi.exe';
$file[]='blabla.exe';usw...
header('Content-Type: text/plain'); # hier muß natürlich der entsprechende MIME-Type hin
header('Content-Transfer-Encoding: Binary');
header('Content-Length: '.filesize($file[$_GET['was_weiss_ich']]));
header('Content-Disposition: attachment; filename='.$file[$_GET['was_weiss_ich']]);
readfile($file[$_GET['was_weiss_ich']]);
?>