As of 0.90.5+, support for running ElasticSearch as a Windows Service is officially included in the Windows distribution.
From the bin folder:
Usage: service.bat install|remove|start|stop|manager [SERVICE_ID]
> service install
Installing service : 'elasticsearch-service-x64'
Using JAVA_HOME (64-bit): c:jvmjdk1.7
The service 'elasticsearch-service-x64' has been installed.
> service start
The service 'elasticsearch-service-x64' has been started