How Can I Hide or Disable Windows Automatic Updates notice

We have some production-floor PCs running Windows XP. They have Automatic Updates turned on (and we want to keep them turned on). But when update files are loaded onto the PCs, they receive a notice that there are updates to install. So users (even after being told otherwise - SURPRISE!!) will tell the system to install the updates. THEN they get a notice to reboot the PC. If they DO REBOOT, it will interrupt processes and equipment controlled by their PCs. And if they DON'T reboot, some updates can cause instability, unitl the PC is rebooted. We want to setup the PCs so that the updates are on the PC, but don't load until the machine is shut down (which happens each night). If we could disable the update notification window, we'd be all set. But we can't find an option which would allow us to do so.