What's the best monitoring framework and tool like Nagios in the MS Windows Environment?

I know Nagios that runs in the UNIX Envirionment. But I can't find one that runs in MS Windows. I prefer freeware or Open Source. But I don't ca开发者_如何学运维re commercial production.

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Take a look on this:

http://en.wikipedia.org/wiki/Comparison_of_network_monitoring_systems

There are many tools like:

ZYRION SOLARWINDS NIMSOFT ZABBIX