Assuming that you have the XML placed on the file system, you might have to perform two steps:
1. Add a new entry in prefill configuration for the file directory.
Navigate to configMgr and search for the default prefill service configuration. Only "crx://" is there by default. You'll need to add an entry for the protocol you are trying. So here you may enter file:///C:/.*
2. Change render URL to dataRef=file:///C:/adobe/data.xml instead of dataRef=C:/adobe/data.xml