Encontrei a resposta na documentação do Apache . Duh.
By default, all Apache services are registered to run as the system user (the LocalSystem account). The LocalSystem account has no privileges to your network via any Windows-secured mechanism, including the file system, named pipes, DCOM, or secure RPC. It has, however, wide privileges locally. Never grant any network privileges to the LocalSystem account! If you need Apache to be able to access network resources, create a separate account for Apache as noted below.