rebooting w2k server

is there a way in w2k server to reboot the server by a time, or a soft ware program.
what we would like to do is have the sever reboot at night when no one is around at a preset time so that we can back up at night at a preset time also, when no one is logged onto the server. our software that we are using will not back up unless everyone is logged off and it will not back up untill it reboots.