Updating stand-alone unmanaged client with .jdb

I have 3 laptops that need to have the signatures updated monthly. I have heard about a solution to add the registry value HKLM_Software_symantec_SMC_TPMState with the dword hexadecimal value of 80. That value creates an "inbox" folder under C:\DocumentsandSettings\All Users\Application Data\Symantec\Symantec Endpoint Manager.When I drop the most current .JDB file in that folder to update the definitions, it creates a new folder in the inbox folder named "Invalid" with my .JDB file inside. Is there a way to make this method work or is there another way to update my stand-alone laptops using the .JDB file. These laptops are running XP with SEP 11.0.6. They have no access to the Internet or any other network. I really dont want to have to make a separate install package every month just for these laptops.