november,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
label {
display: block;
}
.show{
display: none;
}
</style>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<script>
$(function() {
var a = $("form"),
c = $(".checkbox input:checkbox"),
d = $("input:checkbox", a).not(c),
e = $(".show", a);
a.on("click", function(b) {
$(b.target).is(c) && d.prop({
checked: b.target.checked
});
b = $("input:checked").not(c).length;
var a = 5 > b;
$("input:submit").prop("disabled", +a);
a ? e.slideDown() : e.slideUp();
c.prop({
checked: d.length == b
})
})
});
</script>
</head>
<body>
<form action="http://">
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<span class="checkbox">
<label><input type="checkbox" />выбрать/сбросить всё</label>
</span>
<div class="show">минимум 5 пунктов</div>
<input disabled id="button" type="submit"/>
</form>
</body>
</html>