I installed a new Crucial ssd where my optical drive used to be, then tried copying over to it from the original hard drive. There was a problem and not everything was copied, and I made the mistake to tell the computer to boot up from the ssd, even though the install was corrupted .Now my MacBook won't boot up, I've tried command+R, command+v, command+option+shift+delete, and nothing has worked. If there was a way that I could get it to boot up from the original HD, then I could go in and make it the default drive while I fix the problem, but it won't get past the error screen. HELP ME PLEASE!!!