This week's book giveaway is in the Other Open Source APIs forum. We're giving away four copies of Storm Applied and have Sean Allen, Peter Pathirana & Matthew Jankowski on-line! See this thread for details.
If you're trying to do what I think you are, you can't.
Browsers are intentionally designed not to allow a web app to fetch files from the file system.
This is a good thing.
Imagine if any site you went to had the capability to grab files (like you're windows registry) from a hidden iframe without your knowledge.