Working with SharePoint can get complicated. Even seemingly basic tasks are wrapped up in so many layers of automation and support that it can be hard to sort out what you need to do to accomplish your goals. Trying to determine how to change the login page in SharePoint is no exception. For this reason you'll discover how you can modify an out-of-the-box login page to build your own, which you can customize as you desire—including associating it with custom code.
http://www.devx.com/enterprise/Article/35068