I recently purchased a Macbook Pro off of ebay w/o an OS. Now that I am trying to install an OS, I can't get past the grey screen with a flashing folder that has a "?" on it. I've tried holding down the "option" button, this takes me to a grey screen and shows a mouse and nothing more. I've reset the PRAM, and tried many more things I've found online just to get it to show me something... with no luck. **I'm trying to install an OS thats been put on a DVD-R, but to my understanding I should be able to see something on-screen before it comes to whether or not my OS on my DVD-R will work or not!