Inspiron E520 PC Restore

I want to restore my inspiron E520 to its factory state.   the image exists on the hard disk for using Dell™ PC Restore   There's something there.  But when i press (F8) at the begining (before the windows logo) the (repair the computer) option is not there what else can I do to restore the computer to it's factory state.

Can anyone offer any advice?

Thanks