Windows Vista does not have a boot.ini file. Instead, you must edit it under administrator using bcdedit in the command prompt. There is a steep learning curve when using bcdedit, and make sure to backup your current settings as you are messing directly with the registry.
Here is a quick tutorial on editing with bcdedit: http://www.vistaforums.com/FORUM/Topic587-9-1.aspx
Easy BCD simplifies all of this for you. Works with Linux and Mac also!
Get it here: http://neosmart.net/dl.php?id=1