I have a 2007 MacBook Pro running Yosemite from an off the net upgrade from Snow Leopard and the graphics went crazy while trying to watch a TV program on my Slingbox app. I forced a shut down by holding the power button down and now it will not boot up to the hard drive. upon trying to start it up, the initial startup tone is sounded, the apple pops up on the screen and the progress bar begins to load. Upon reaching about half way on the progress bar it stops loading and eventually goes to a black screen with an arrow cursor. I tried reloading the OS with the original Snow Leopard OS disc but got a pop up stating that the OS was not compatible. I then went to utilities and ran a disc permissions test, a disc permissions repair , and then a disc test but the it said the disc appeared to be OK. It still will not boot and is still only loading about half of the loading start up bar. Anybody have any ideas? I think the hard drive may be toast but I really would love to load some of the pictures and desktop info on to an external drive but don't have a clue on how to proceed.

[![enter image description here](https://i.stack.imgur.com/9KGGD.jpg)](https://i.stack.imgur.com/9KGGD.jpg)