I have two 2008 MacBooks and my first one I upgraded my tiny 160gb hard drive to a 750gb Western Digital Scorpio Blue 5400 rpm SATA drive. EASY! No problems, and new drive works great. Now, the second MacBook I bought had a 250gb hard drive and I bought a 500gb Western Digital Scorpio Blue 7200 rpm SATA drive. I did the exact same process as before by cloning my hard drive with Super Duper and I tested the new cloned hard drive by booting my MacBook up and holding down the "option" button to boot from the usb connected cloned hard drive. It booted up a bit slow, but fine. Everything was on there and working. Then I took the old 250gb hard drive out and put the new 500gb hard drive into the MacBook. Turned on the MacBook and got a blank screen, then a file folder with a question mark in it. I had now idea what was wrong. Then I switched back to the 250gb hd, rebooted the Mac, and works great. So after this, I recloned the drive with Super Duper again. Tested it again and it booted. Then switched the two drives in and out of the MacBook again. SAME THING! I get a folder with a question mark. Can anyone tell me what may be wrong? Please?