My hard drive passed away a little while ago, so I bought a new hard drive: a Hitachi Travelstar 500GB 5400RPM HD. I hooked it up as an external hard drive and used Disk Utility to format it and installed a clean Mac OS X. When the drive is in an external enclosure and connected to the computer via USB, the computer boots up fine and Mac OS X loads up just dandy. However, when the drive is being accessed internally via the hard drive cable, the computer doesn't recognize it. I've tried holding Option on start-up. I doubt that it's the hard drive cable, because it seemed to working fine when the drive died. What are some other things that I can try? Help would be much, much appreciated.