Here is a quick query, it will give you model, serial number and primary user.

SELECT T1.[Computer Model] AS 'Computer Model', T1.[Serial Number] AS 'Serial Number', T0.[User] AS 'User' 
FROM [Inv_AeX_AC_Primary_User] T0 INNER JOIN [Inv_AeX_HW_Serial_Number] T1 ON T0.[_ResourceGuid] = T1.[_ResourceGuid] 
WHERE T1.[Serial Number] LIKE '%'

When I run a query with that expression, it gives me an error - are there additional parameters?

Incorrect syntax near the keyword 'SELECT'.

Maybe you had some superfluous character or line before the code when you cut and pasted the SQL into your report window.

The query is simply working fine. But i think we need to display unique records. For that i used DISTINCT and also MACHINE name just in case you want see that in the report

SELECT	DISTINCT(T0.[User]) AS 'User', T2.[Name] AS 'Machine Name', T1.[Computer Model] AS 'Computer Model',T1.[Serial Number] AS 'Serial Number' 
FROM [Inv_AeX_AC_Primary_User] T0 
INNER JOIN [Inv_AeX_HW_Serial_Number] T1 ON T0.[_ResourceGuid] = T1.[_ResourceGuid] 
JOIN vComputer T2 ON T1.[_ResourceGuid]  = T2.Guid
WHERE T1.[Serial Number] LIKE '%'
AND T0.[Month] =  datename(month, getdate())