>>I'm talking about the FTP server that appears in the IIS management. The place where we assign virtual directories, etc.
>>
>>I'll verify if I have done what you suggest.
>
>If this still doesn't work, I suggest troubleshooting as follows:
>
>1. Create a local group called FTP Test.
>2. Add a non-admin user to that group.
>3. Set the permissions on a specific FTP directory to allow change privileges to that group using Windows Explorer.
>4. See if that user can get in. If so, you're fine. If not, it's an IIS setting problem.
>
>Also this depends on how users are accessing FTP. If via browser, they have to type in user name and password as part of the URL, even if they have authenticated on the HTTP side.

In my case, it's pure FTP using WSFTP32. I also tried with other FTP mecanisms and it's all the same problem. The file get locked after a download. I'll apply what you suggested and will let you know.