File upload is not working in IE9

Is that on localhost in a WAMP/XAMPP environment or on an Apache server? Does that problem only exist in IE9? Do you get an error message?

If you are on XAMPP/WAMP, see this post: Mime type issue (again). It’s a known issue.

Edit: Is there a special reason why you are still using an old browser like IE9? Microsoft has stopped supporting IE 9 in January, so there will be no security updates anymore.