You can do that by adding a filter criterion on
tblAssets.Assettype. It is -1 for Windows assets.
Select Top 1000000 tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.IPAddress,
tsysIPLocations.IPLocation,
tblAssets.Lastseen,
tsysOS.Image As icon,
tFileVersions.Found,
tFileVersions.FileVersion,
tRegistry.Value As Datum,
t2Registry.Value As Tid
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Left Join (Select tblFileVersions.AssetID,
tblFileVersions.Found,
tblFileVersions.FileVersion
From tblFileVersions
Where tblFileVersions.FilePathfull Like '%SCClient.exe') tFileVersions
On tblAssets.AssetID = tFileVersions.AssetID
Left Join tsysOS On tblAssets.OScode = tsysOS.OScode
Inner Join tsysIPLocations On tblAssets.IPNumeric >= tsysIPLocations.StartIP
And tblAssets.IPNumeric <= tsysIPLocations.EndIP
Left Join (Select tblRegistry.AssetID,
tblRegistry.Value
From tblRegistry
Where tblRegistry.Valuename Like 'SCCMLastRunDate') tRegistry
On tblAssets.AssetID = tRegistry.AssetID
Left Join (Select tblRegistry.AssetID,
tblRegistry.Value
From tblRegistry
Where tblRegistry.Valuename Like 'SCCMLastRunTime') t2Registry
On tblAssets.AssetID = t2Registry.AssetID
Where tsysIPLocations.IPLocation Like 'EDU.IFM.LIU.SE' And
tblAssetCustom.State = 1 And tblAssets.Assettype = -1
Order By tblAssets.AssetName