vComputer only contains computers with an 'Active' status. IsManaged = 1 is still true for 'Retired' computers as well so that won't be sufficient.
Try this:
SELECT T0.[Name] AS 'Name', T2.[OEM OS] AS 'OEM OS', T0.[OS Name] AS 'OS Name', T1.[OS Type] AS 'OS Type', T3.[System Type] AS 'OS Version', T0.[OS Revision] AS 'OS Revision', T4.[ProductSuite] AS 'ProductSuite', T0.[System Type] AS 'System Type'
FROM vComputer T0
INNER JOIN [Inv_AeX_AC_Identification] T1
ON T1._ResourceGuid = T0.Guid
LEFT OUTER JOIN [Inv_LPH_Asset_Details] T2
ON T1.[_ResourceGuid] = T2.[_ResourceGuid]
LEFT OUTER JOIN [Inv_AeX_OS_System] T3
ON T1.[_ResourceGuid] = T3.[_ResourceGuid]
LEFT OUTER JOIN [Inv_IUH_SW_WinVer] T4
ON T1.[_ResourceGuid] = T4.[_ResourceGuid]
WHERE T0.IsManaged = 1
ORDER BY T0.[Name] ASC