System restore. ok, I do know how to use the system restore action, but, I want to redo my

Question

ok, I do know how to use the system restore action, but, I want to redo my computer to when it was new again. I've done this before by pressing a button before setup. I think it was one of the F's but i dont remember. On the top left of the screen it says 'Setup=F2 Boot menu=F12 I know how to get to the boot menu and it does not have any option to redo my pc.