For full details see: http://www.windows-noob.com/forums/index.php?/topic/7022-last-logged-user/
Select R.Netbios_Name0, R.User_Domain0 + '\' + R.User_Name0, CS.UserName0 from dbo.v_R_System R join dbo.v_GS_COMPUTER_SYSTEM CS on R.ResourceID = CS.ResourceID join dbo.v_FullCollectionMembership FCM on R.ResourceID = FCM.ResourceID Where FCM.CollectionID = 'SMS00001'