In the absence of Lansweeper updating I have written this report SQL which should hopefully help others in the same position as described above. It will show all PCs without AntiVirus and any PCs with Windows Defender with realtime scanning turned off. Please note that I don't know if this definitely works on Vista as I don't currently have a machine to test with but it works perfectly on my Windows 8 boxes and Windows 7 boxes (Mix of defender, Security Essentials and Symantec).
Goto: Configuration > Custom Scanning
Choose Add registry key to scan
Rootkey: HKEY_LOCAL_MACHINE
RegPath: SOFTWARE\Microsoft\Windows Defender\Real-Time Protection
RegValue: DisableRealtimeMonitoring
Then either create a new report or edit the existing AV report with the below SQL.
Reports accessed via Dashboard > All Reports (or report builder)
Select Distinct Top 1000000 tblAssets.AssetID,
tblAssets.AssetUnique,
tblAssets.Domain,
tblAssets.Description,
tblAssets.Lastseen,
tblAssets.AssetName,
tsysOS.Image As icon
From tblAssets
Inner Join tblComputersystem On tblAssets.AssetID = tblComputersystem.AssetID
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysOS On tblAssets.OScode = tsysOS.OScode
Inner Join tblRegistry On tblAssets.AssetID = tblRegistry.AssetID
Where (tblAssets.AssetID Not In (Select tblSoftware.AssetID
From tblSoftware Inner Join tblSoftwareUni On tblSoftwareUni.SoftID =
tblSoftware.softID Inner Join tsysantivirus On tblSoftwareUni.softwareName
Like tsysantivirus.Software) And tblAssets.AssetID Not In (Select
tblRegistry.AssetID From tblRegistry
Where
tblRegistry.Regkey =
'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender\Real-Time Protection' And tblRegistry.Valuename = 'DisableRealtimeMonitoring' And tblRegistry.Value != '1')) And tblComputersystem.Domainrole < 2 And tblAssetCustom.State = 1
Order By tblAssets.AssetName