After installing nagios3 on Ubuntu 10.04 I needed a couple of configchanges.
After reading this, I would suggest the following:
Download a msi installer for nsclient from here. In that way you don’t have to install the service manually.
Check windows machines with: /usr/lib/nagios-plugins/nt.cfg
– Remove the ‘ characters
– specify port: 12489
– Expand commandline with: $ARG2, $ARG3 $ARG4
– Change ‘windows-server’ to ‘generic-host’