I have tried zapping the pram, nvram, unable to boot from a disk, tried safe mode, tried verbose, did the single user /sbin/fsck -fy several times and it came back with everything appears OK. Tried the hardware test & no trouble found, did the short & long test. The MacBook is a college kid (friend of my youngest) that dropped it off last night and I am stumped. I thought it was surely the HD but all the test say it is fine. I cannot get it to boot from a disk either. Any clues.