I searched for hours and hours, days on end, hundreds of posts and dozens of websites. All I wanted was to force the open/save dialog box so people could save my files instead of them opening automatically within the browser/plug-in. I found lots of clues and advice and technical jargon, but never found a step-by-step explanation for a dummy.

Thanks to Musicman, I finally got it working. I take no credit for this, but here is a STEP-BY-STEP explanation for the uninitiated, hopefully saving you many steps and hours of searching. I'm sure this is overly simplistic to those who know what they're doing, but for those of us clueless, it does what I needed it to do and nothing more.

I happened to settle on using php script to do this because it was the easiest for me to understand, and my website host supports php.

I opened a simple text editor like Notepad, and typed the following:

<?
header ("Content-Type: application/download");
header ("Content-Disposition: attachment; filename=$yourfile");
header("Content-Length: " . filesize("$yourfile"));
$fp = fopen("$yourfile", "r");
fpassthru($fp);
?>

Now 'Save As...' and call it download.php (make sure it does not put .txt on the end of the filename). The phrase $yourfile is a variable that you'll define in Flash (the next step) as the name of the file you want people to be able to save.

In your Flash movie, select the instance of your button that is supposed to activate the download procedure, and open the Actions panel. The ActionScript here needs to direct the browser to your download.php file, and set the variable (yourfile) as the filename you wish them to download.

Mine looks like this:

on (release) {
getURL ("download.php?yourfile=samplesong.mp3");
}

On releasing the mouse button, the browser goes to download.php, with the variable yourfile set as samplesong.mp3, which is the file I want people to be able to save (yours will be different, of course). The variable gets passed to the php file (called $yourfile) which does the rest.

The way I have done this, the php file, the file I want downloaded, and my flash files all have to be in the same folder. So upload everything to your webspace folder and test it.

Apparently you can separate the files into different folders, you just have to specify in your flash and/or php file. For example, if the flash and php files are in your root, but your downloads are in a folder called downloads, you'd replace $yourfile with downloads\$yourfile.

I am not 100% sure how many platforms/browsers this works for, but I have tested it on Win98, Win98SE, and WinXP with no problems in the following browsers:
IE6
Netscape7.2
Mozilla 4
SlimBrowser 4.04
AOL 9.0

Apparently it is supposed to work with Macintosh browsers, but I have no way to test this. If anyone knows specifics about php headers in Apple OS browsers, I'd love to be reassured that this will work.

Thank you so much for your help, Musicman. I'm sure any errors are mine alone. If anyone sees glaring errors or problems with this procedure, please post it. I tried to keep my php file exceptionally simple because I'm a dummy. I'd be happy to include valuable additions to it if you explain them to me.

Hope this helps.