backup script to automate backup on NT

I've installed Informix Online Workgroup server on a PC with Windows NT 4.0. In order to automate the backup process, I created a 'backlog.bat' file which goes like this: cd c:\\informix setenv cd bin ontape -a When I schedule the job using the 'at' command: at 12:00 backlog.bat I get the message "user not a member of informix-admin" I set the schedule service to run as a system account. Since I am logged in as Administrator, which is a member of the informix group, the 'at' job should run with any necessary permissions. The schedule service is in interactive mode. I can run ontape -a fine on the command line (again, I am logged in as administrator). Any help is welcome. Thanks