Open "Registry Backup" go to "Settings" click on "Edit Schedule" go to "Task Scheduler Library" and double click on "Tweaking.com - Registry Backup" if it is there! (If not click on "Create Schedule" under "Settings" in "Registry Backup")
In "Properties for Tweaking.com - Registry Backup" choose "Triggers" edit and "Start activity" change to "On a schedule" and change to what you want. Then click ok and ok again.
This is for win 7 and vista (I think)
Tomas