memcache on Windows is complicated so you have 2 options, either install memcache (the bad option) or disable memcache (good option)
in file /backend/config.php check settings for cache
PHP Code:
// Caching settings
$site_config["cache_type"] = "disk"; // disk = Save cache to disk, memcache = Use memcache, apc = Use APC
$site_config["cache_memcache_host"] = "localhost"; // Host memcache is running on
$site_config["cache_memcache_port"] = 11211; // Port memcache is running on
$site_config['cache_dir'] = getcwd().'/cache'; // Cache dir (only used if type is "disk"). Must be