How do I list users on a Windows host?

For WMI plugin, the following will create a basic sampler that has a row for each user on the system:

<sampler name="WinUsers">
<plugin>
<wmi>
<columnMode>
<columns>
<class>
<data>Win32_ComputerSystem</data>
</class>
<column>
<member>
<data>UserName</data>
</member>
<displayName>
<data>Username</data>
</displayName>
</column>
</columns>
</columnMode>
</wmi>
</plugin>
</sampler>

The result will be as follows:

From this you can now add for example a column with a rule to alert if the rowName is allowed or not allowed on the host, or you can set a simple rule on the instances headline to count users, for example the criteria being that value > 0.