from an old DNN FAQ -

Q. What permissions are required for DNN to function properly under W2K?

A. The ASPNET account (which is the account used for running the asp.net worker process) must have FULL permissions on the WEBROOT and all subfolders for the DNN application. There are several conditions where the application writes files both to the root (e.g. child portal folders) as well as to subfolders (e.g. uploading portal files).

** Important note ** Under W2K only, the ASPNET process must also have READ ATTRIBUTE privileges (not read file) on the DRIVE ROOT (e.g. D:\) for the DirectoryInfo class in .NET to work correctly.

>>> If you're on W2K, make sure your administrator understands your asking for READ ATTRIBUTE privileges... not read file (which would be a security issue).