By default the Overwrite checkbox in Upload.aspx is checked in WSS 3.0 and MOSS 2007, but sometimes you may want to change this default.
MOSS junkie has a post on how to change that default.
But his solution has the downside of having to modify one of the standard application pages which is unsupported and may be overwritten by a upgrade
So how do we change the default without modifying upload.aspx?
Once again the <delegate> controls in the default masterpage can help us.
This time it's the AdditionalPageHead delegate we can use. This delegate allows you to add any number of usercontrols to the page header of every page in sites where your feature is activated.
So we add a feature with the following elements.xml file:
<?xml version="1.0" encoding="utf-8" ?>
<%@ Control Language="C#" %>
var inputs = document.getElementsByTagName('input');
var input = inputs[i];
if (input.type == 'checkbox'
input.checked = false;
All the source is here and if you just want a solution file it's here