For all those who have installed both Windows 7 and Windows 8 dual boot and no longer able to access at least boot after restarting Windows 8, Then this article is for you.
this problem exists because Windows 8 with the "Hibernate" does not turn off the computer so I defined the PC and this causes the inability to access the boot panel.
To resolve this problem you should read and correctly perform the steps listed below the article. So now we have turn off the Hybrid Boot ,To do this simply go to the Start menu, and try power button, as you can see from the image.
At this point you should click on Change Settings That Are Currently unaviable (to view you must have User Account Control active), and remove the V to Enable Hybrid Boot (recommended) at the bottom.
After performing these steps the problem should be gone, well commented for more information