I wanted to add some checks to a Windows server and the methods seem to have changed a little over the years. At the moment I have amended the nsclient.ini file on the Windows box with:
CheckDisk=1
CheckSystem=1
Then from the Nagios box I can check CPU with a threshold as follows:
/usr/lib64/nagios/plugins/check_nrpe -H winserver001.domain.tld --command check_cpu -a "warn=load > 96" "crit=load > 99" "time=5m"
We can also check windows performance counters with:
/usr/lib64/nagios/plugins/check_nrpe -H winserver001.domain.tld --command check_pdh -a "counter=\Memory\Available MBytes"
There is useful info here on available checks and options.