Honestly speaking, I myself am not sure what I am try to doi

just kidding.
What I want to do, is to HIDE the "f" parameter given to the script, if some hacker/leecher etc etc knows the filename (even without extension) it is easy for him to search for direct link etc. I've heard of things like mod_rewrite etc. But i am unfamiliar with them. OR alternatively, if there was a way, to make this work:
.... download.php?f=fdcu39sdu&fc=5sd8al0.4a2
which will then force the download of song SPECIFIC TO THE ID "fdcu39sdu" and save it to specifi filename to "5sd8al0.4a2"
I am not familiar with PHP, but i am familar with programming in general. (have to start learning PHP soon though). reading your script, I can guess that SOMETHING like this MIGHT work:
$search = $_GET['f'];
if ($search = "fdcu39sdu")
$original = "Some file name";
else if ($search = "d58dasf45")
$original = "Otherfile etc";
......
So can you please help on this .
Thanks