Just a very quick post that might help somebody stuck in the hell of having php.ini not recording your changes to the include_path. Here's some things to check.
1) shut off apache to edit the file.
2) make sure you have permission to edit the file. you might have to change permissions. check to see if you're writing to the file by checking the time the file was last updated.
3) if you've installed pear check to see if pear didn't add something to the php.ini file near the bottom. it's basically another include_path configuration. since there can only be one it will override the one at the top of the file. simply add your changes to the one configuration are and you should be good to go.
4) another thing to check is whether you can write to the file in another configuration option. just throw something down and restart apache and check it. if you can write to the file but just not see include_path then you have another include_path somewhere in the file that's overriding your settings.
5) the other obvious thing is to check to make sure the php.ini file is the one that's being loaded. do this by looking in the phpinfo() file. you can add this to a php file and run it in htdocs or wherever your root is, or in the case of xampp just run localhost and find the phpinfor() on the left bar.
hope this helps.