Hi,
I want to discover computers which don’t have a specific property
I understand that on Web Reports, it is showed as
I’ve tried to search contains and there is no result.
I’m missing someting. Please help 
The value isn’t actually ‘<not set>’ - that’s just a placeholder to indicate that there is no value.
So what I need to select to show computer which don’t have this property set
Export the full result with no filter and open it in Excel/notepad, check one of the machines that it displays the “<not set>” placeholder and the report will show what it is actually underneath. Once you have the actual value you can re-add your filter and use it in it.