You probably just need to get the extension DLL for APC on Windows... Not to sure though. All I know is that PHP 6 will have it in PHP by default (Enabled by default too IIRC)
It seems it's now using the php.ini inside the php directory.
php_apc.dll wasn't listed under the windows extension area, but php_apc.dll is in the ext dir.
I added "extension=php_apc.dll" but when I restart apache it gives the error:
PHP Warning: PHP Startup: Unable to load dynamic library 'C:\xampp\php\ext\php_apc.dll' - The specified procedure could not be found.\r\n in Unknown on line 0