Simon,

If the "IIS/Windows 2003 Image" checkbox is marked, SetupBuilder compiles "cluster" files without any extension. In this case your ISP has to add a MIME type so files without extensions can be downloaded from your server. Then you need a MIME type to download the Server Manifest File. You can use any extension for your Server Manifest File (e.g. .txt, .ini, .xxx).

Does this help?