How Do I Use ASP To Download A File That Has Particular Ntfs Permissions

I'm trying to write a script that will allow validated users to
download a file that has specific ntfs permissions. Here's a summary:

Scenario:
1) The name of the file is "binary.zip".
2) I've created a local account on the server called "dl_user".
3) dl_user is the only account that has permissions on binary.zip.
4) I've written a script that validates several people to access a web
page that has a link to binary.zip. However whenever they click it,
they get prompted for a username and pw. If they enter the "dl_user"
credentials, it works.

Problem:
I don't want these people to be prompted for the username and pw.
Instead, I'd like IIS, through some ASP mechanism, to pass the dl_user
credentials in the background so that the users are completely unaware
of the account that has NTFS permissions to the file. Is there any way
to do this?