In order for your exchange members to upload banner images, the proper permissions must be set on the MemberBanners folder.  Uploading files requires write permissions for the Anonymous Web User.  The changes are quite simple but unless you have complete access to the web server, the changes must be made by your Web Hosting Provider.

First, use File Manager to find the MemberBanners folder.  Note that this is done in file manager and not the Microsoft Management Console.  Once the folder is located, right mouse-click on the folder and select Properties.

The following dialog box appears.  Select the Security folder.  Next, click the Permissions button.

Next, select the Anonymous User Account and set the Permissions to Special Access. Double-click on the anonymous user and select only Read and Write.

Click OK until all the dialogs unload.

Very Important:  You must now turn off Script access to this directory.  The way to accomplish this depends on what publishing software you are using or what level of access you have to the web server.  One way to do this is the the MMC in IIS.  If using FrontPage, you can right-click on the directory and uncheck the option for "Allow Scripts to be Run".  If you do not do this then users can easily HACK into your site.  For example, a user can upload a damaging script, execute it on your web site and delete the entire thing.