KeeperWar, cамое простое в виде отдельного приложения не сторонними средствами,
test.hta:
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="x-ua-compatible" content="ie=9">
<title>Test</title>
<hta:application applicationname="test" navigable="yes">
</head>
<body>
<form name="test">
<input name="user"><button>Save</button>
</form>
<script>
document.test.onsubmit = function () {
var fso = new ActiveXObject('Scripting.FileSystemObject');
var txt = fso.OpenTextFile('test.txt', 8, true);
txt.writeLine(new Date + ' | ' + this.user.value);
txt.close();
};
</script>
</body>
</html>