You mean on the Windows server? The answer is in the error:
NSClient - Error: Invalid Password.
When you set up your check_nt command, you need to include an option for the password (secret), if you don't use a seperate line for each host, you'll need to make sure when installing NSClient++ to use the same password on all servers:
# 'check_nt' command definition
command_line $USER1$/check_nt -H $HOSTADDRESS$ -p 12489 -s <password set up on NSClient> -v $ARG1$ $ARG2$
Or the nrpe ones? Those are because either your nagios plugins on the client, or the nrpe plugin on the server isn't installed to use ssl, and the other is. Either both need to be configured with ssl, or both need to be configured without.
Your timing of posting this is actually funny to me. Monday I had to learn how to get Nagios up and running as we're looking at possibly using that to monitor our servers. So I've been troubleshooting issues like this non-stop the last 3 days and have learned ever so much about nagios and the configuration. Still haven't figured out how to get check_nt to check disk i/o though. Got it working on linux through check_iostst, but total failure so far in Windows.