Index: wp-admin/users.php
===================================================================
--- wp-admin/users.php	(revision 21421)
+++ wp-admin/users.php	(working copy)
@@ -188,6 +188,34 @@
 
 	include ('admin-header.php');
 ?>
+<script type="text/javascript">
+jQuery(document).ready(function($){
+	
+	// Disable submit button initially
+	$('#submit').attr('disabled', 'disabled');
+	
+	var delete_option0 = $('#delete_option0'),
+		delete_option1 = $('#delete_option1');
+
+	//Enable submit button when user selects either option
+	delete_option0.on('change.confirm_delete_user', function(){ updateFormEnabled(); });
+	delete_option1.on('change.confirm_delete_user', function(){ updateFormEnabled(); });
+	
+	
+	function updateFormEnabled() {
+		
+		//enable the submit button
+		$('#submit').removeAttr('disabled');
+		
+		//stop listening to changes
+		delete_option0.off('change.confirm_delete_user');
+		delete_option1.off('change.confirm_delete_user');
+	}
+
+});
+
+
+</script>
 <form action="" method="post" name="updateusers" id="updateusers">
 <?php wp_nonce_field('delete-users') ?>
 <?php echo $referer; ?>
@@ -214,7 +242,7 @@
 <?php if ( $go_delete ) : ?>
 	<fieldset><p><legend><?php echo _n( 'What should be done with posts and links owned by this user?', 'What should be done with posts and links owned by these users?', $go_delete ); ?></legend></p>
 	<ul style="list-style:none;">
-		<li><label><input type="radio" id="delete_option0" name="delete_option" value="delete" checked="checked" />
+		<li><label><input type="radio" id="delete_option0" name="delete_option" value="delete" />
 		<?php _e('Delete all posts and links.'); ?></label></li>
 		<li><input type="radio" id="delete_option1" name="delete_option" value="reassign" />
 		<?php echo '<label for="delete_option1">'.__('Attribute all posts and links to:').'</label>';