HDD problem. Need some answers.

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My friends computer just went.  Nothing on the screen, won't boot etc.  I have checked memory, vid card, etc.  I know it must be the hdd because I put one of my hdd in and it started to boot.  Different drivers so some things would not work but that showed the vid card worked along with everything else except the hdd.  My problem is the hdd works when I attach it to my computer.  I can see all the folders etc.  I tried to clone and see if that would work but when I put it into their computer it would not boot.  When I did a clone one screen came up and said it could not read some sector.  What can I do now that the old hdd is cloned?  I did keep all info on the old hdd also.  Any advice would be greatly appreciated.