File download script code something like Rapidshare, Hotfile, etc.

Goal #1: To allow a visitor at a web site to download a file Goal #2: To prevent robots and direct external links from downloading the file Requirements: 1) The file to be downloaded will reside in a non-public location. That is, there will be no permanent URL to the file that is being downloaded. This is because we do not want the direct link to the file to become public knowledge. 2) If there is an easy way to have the scipt/code know when the download is complete, and then delete the temporary file (should one exist), this would save us from having to create a scheduled batch file to delete any temporary files. 3) A doorway form must be used before being given access to the file. The doorway page needs to use a math based CAPTCHA form before allowing the download to take place. The type and complexity of the match CAPTCHA will need to be discussed 4) An internal global variable that will define whether the CAPTCHA will be used or not. The server on which the code (and downloadable file) will reside will be either Windows 2000 Server or Windows 2003 Server. ActivePerl and ASP (not .NET) are available on these servers. NO PHP! NO LINUX!