Hi, group policy is designed exactly for your purpose: automatically change settings for a number of machines. Even I find it very strange not to modify group policy some specific cause may exist to do so. In this case you should look for registry settings responsible for the specific task and change it. In most cases registry modification of system settings require a system reboot, maybe this is why it "doesn't work" for you. It looks like you are installing the system from scratch so one more or less reboot should make no difference. A number of websites describe lot of different registry settings try google for "windows unattended"

Take care if you change windows registry, if at some latter point you decide this changes don't fit your requirements anymore you need to adapt all systems again. Using a group policy you just need to change/remove a policy.