This post focuses on new Trigger Start Services in Windows 7. A trigger-start service’s a regular service that you can configure to run (or stop running) only when its triggered, that’s, only when certain criteria and conditions that you define’re met (for e.g., when first network IP address becomes available, or when last network IP’s lost). Here’s a list of available triggers that you can use to configure Start-Up mode of a given service: Device interface arrival or departure; Joining or leaving a domain; Opening or closing a firewall port; Group policy change; First IP address available/ last IP address leaving; Custom event – Event Tracing for Windows (ETW). Last item in the list represents extendibility point. As a developer, you can configure any ETW event as a trigger for services, which gives you a very good tool to fine-tune your control over starting and stopping services from your application.
Full Article: Windows blog