With much appreciation to Amit.rk3 for his answer, I modified his answer(which I would have put in comments, but I dont have 50 points!!). The OP did say clear a selected file, so I would assume a single input. I have a rather long and complex page, so I wanted to be very specific which input to reset.. The code below works perfect on IE(8) and FF ESR :)
Select Photo(optional): <span id="form_sp"><input id="file" type="file" size="40" name="photo"/></span> <button id="reset_t">Reset file</button>
<script>
$(document).ready(function(){
$('#reset_t').click(function(e) {
e.preventDefault(); // keeps form from submitting
$("#form_sp").html('');
$("#form_sp").html('<input id="file" type="file" size="40" name="photo"/>');
});
});
</script>