I installed a new hard drive, connected my old hard drive via USB. Now I'm trying to start my MacBook to my USB drive to transfer file & system, however I'm unable to do so. Holding the Option key, or Command R key down after the chime doesn't do anything-- I just get a blank screen. Note: I'm not experienced in the Mac world! How can I select the USB as a startup disk? Putting back my old drive will require me to break the cover - bad screws... Thanks.