SQL Query question (items not having some value in a column)
I believe the following query will give you the right computer name

 select ComputerName from dbo.computers
 where os= 'windows 7'
 except
 select ComputerName from dbo.computers
 where os= 'windows 7'
 and appname not in (select appname from dbo.computers where os='windows 10')


The result is: