Here is what I have in my PHP.ini:
extension=php_apc.dll
...
[APC]
apc.enabled = 1
I'm running Apache 2.0.59, PHP version 5.2.3 on Windows Server 2003.
I've already installed XDebug compiled with vc6. Thus, I got the APC version 5.2 vc6. Here are both filenames that I downloaded (and put the *.dll in php/ext/).
php_apc-3.1.5-5.2-vc6-x86.zip php_apc-3.1.5-5.2-nts-vc6-x86.zip
I got them here.
I've tried rebooting the server and in both cases, I get the following error:
PHP Warning: PHP Startup: Unable to load dynamic library './ext/php_apc.dll' - The specified module could not be found.\r\n in Unknown on line 0