You will need to set the permissions for the IUSR_ account to Read/Write/Delete (Modify) for the following folders in your Site Store Professional installation directory so will be able to upload content such as product images from the web-based admin system:

store_content\
includes\common\lib\file_upload\Temp\

 The permissions can usually be set in your hosting account control panel. Please contact your webhost support if you cannot set the permission from your control panel. (Note: The permissions must be set on the \store_content\folder to “propagate” or “inherit” to all subdirectories inside the \store_content\ folder. )

If you need assistance setting the folder permissions on your webserver, please call (800) 974-6493 Ext 2 or email support@sitestorepro.com