The simplest way is to insert wp_list_pages("title_li=") into your header.php. This outputs an unordered list of your pages. Then you can use suckerfish or superfish or whatever to turn that into a dropdown menu :-)
If it's not dynamic? You mean it's just HTML? HTML works in Wordpress themes (or any .php) same as normal so you should be able to just copy and paste it.
Hope that helps
David.