What tool do you use to monitor your servers?
is there a free, open source server monitoring tool like Nagios that runs on the MS stack? It will need to be able to detect service stoppages and starts also.
Polymon is exactly what you're looking for.
It's fantastic for monitoring anything that can be communicated by TCP Port, SNMP, Powershell, WMI, SQL, HTTP, Perfmon, or Ping.
I don't monitor anything *nix, so I can't speak to that. But for the Windows world it's very simple to set up, extremely intuitive, and extremely flexible, It has very nice built-in dashboard display, sms or email notification. You can do long-term trending/reporting/graphing, auto respond to events (like restart a service if it stops, etc.)
And at least for me, it's a lot easier to set up and maintain than Nagios, OpenNMS, or Zabbix. I heartily recommend it.
Spiceworks is a complete network management and monitoring, helpdesk, PC inventory and software reporting solution to manage everything IT in small and medium businesses.
You could look at Cacti
It's more geared towards network graphing but has add-ons for alerting and thresholding.
Hyperic offers a pretty good solution. http://www.hyperic.com/products/open-source-systems-monitoring.html
You could also give Just for Fun (http://www.jffnms.org/) a try, we have used that to monitor quite a few different things over the years. It can be a bit tricky to get going but its powerful once its running
You may consider using Total Network monitor- it's free and easy to use with a very nice interface. It can monitor services, alert you via email or messages, log in event log and take actions when a service fails. There are also many other monitors- you do not need to install any agents.