I need LOTS of help

Problems are with the FTP site. Running NT server 4.0 with IIS 4.
Somene has uploaded some files to the ftp directory, which is unsecured with anonymous logon. These files cannot be deleted from windows or ms-dos. These files can be viewed, but cannot be altered in any fashion. The files are in a tree that is five levels deep, trying to delete or move any files or folders results in the same message. The message is that the file could not be found.
The files appear to be some pirated sw for a warez site.

Anyone have any idea what is going on here?

Also, the FTP site cannot be accessed with any account, including admin, from a browser. The anonymous access no longer works.
I have created a new ftp root with new security and reset all ftp access properties with the same results.
Also there is someone who is constantly connected to the ftp connection. If I close the connection it reappears within 5 seconds. If I deny access to that IP address the same account logs in under a different IP in a few minutes.

Any ideas on how to free up the ftp site, and get rid of this attack?