I'm running Windows version of Apache with php as module. System is Windows XP Service Pack 2 on NTFS filesystem. To avoid potential security problems, I've set Apache to run under NT AUTHORITY\Network Service account, and there is only one directory, named Content, with Full Access for this account. Other directories are either not accessible at all or with readonly permissions (like %systemroot%)... So, even if Apache will be broken, nothing would happen to entire system, because that account doesn't have admin privilegies :)
