Memcached 1.4.5 binary for win x64 can be found here: http://downloads.northscale.com/memcached-1.4.5-amd64.zip
Another option would be to install Couchbase Server 1.8.0 x64 from here: http://www.couchbase.com/download, the bundled memcached seems to be version 1.7.1.1 (sounds like an internal version, I can't tell which is the real one)
As for running memcached as a service, this tutorial might be enough:
http://www.richardnichols.net/2010/08/install-memcached-on-windows-server/
