In SharePoint 2010 the Customize Form button in the List Settings enables you to start InfoPath 2010 and edit the form. This button only works offcourse when InfoPath 2010 is installed on your computer.
In the case that this button is not working (you click the button, nothing happens.. not even an error message) your SharePoint site is not trusted by the operating system.
To solve this:
- Add the URL of your site to the Trusted Sites
- Close the browser and re-open it
- Now your Customize Form button will start InfoPath 2010
