NT 4.0 Anonymous FTP permissions

In NT 4.0 with IIS that came with option pack 4. Able to anonymous logon and FTP to selected directories and download files but unable to upload and/or delete files.

Verified “write” selected on main FTP server permission for home directory and also selected “write” on each virtual home directory and those FTP sites with specified IP addresses. “Allow Anonymous Connections” is checked under Security tab of MMC. Receiving error code 550 when using FTP client (CuteFTP).

I need to adjust this FTP server to allow files to be uploaded and deleted. What am I missing?