Have the script run as a windows service, which is the rough equivalent to a *nix daemon, so there is no possibility of user interaction. I have had good success with this for similar scripts. Download the "Resource Kit" from somewhere on Microsoft's site, which contains the utilities instsrv.exe and srvany.exe that allow you to install a service. There are lots of how-to documents for this procedure.
Here's one to get you started: