Nagios - NSClient++ cannot run included external script
As krisFR pointed out you need to prefix vbs file with cscript.exe (and various other options) .
Script in windows does not work like scripts in unix so they are not "runnable" by them selves (ish). Thus all scripts has to be prefixed with their runtime.
In theory this should be documented here: http://docs.nsclient.org/howto/external_scripts.html#languages but I see it is missing so I shall try to update it ASAP.
check_updates=cscript.exe //T:30 //NoLogo "scripts\\check_updates.vbs"
Another way to resolve this is to use the so called "wrapped" scripts in NSClient++ then you can define "macros" for how various extensions are executed:
[/settings/external scripts/wrappings]
vbs=cscript.exe //T:30 //NoLogo %SCRIPT% %ARGS%
[/settings/external scripts/wrapped scripts]
check_updates=scripts\check_updates.vbs
More details can be found here: http://docs.nsclient.org/howto/external_scripts.html#wrapped-scripts