Cannot access files on external HDD

Hi all

Have eventually managed to access my external HDD, however now that I have gotten there I cannot open any of the files its as if they are not accessible, firstly the drive did not function, when I mean not function the light stayed on or went off but I could not access it, now after running chkdsk P: /R /F it works, so then I tried disk clean up and it cleaned the disk and compreessed a load of files, then I tried to defrag it to no avail, just would'nt let me do it, when I tried to access the files could'nt not even read only, there are a variety of files e.g. word, excel, power points, windows media, cannot access any of them, can someone tell me what has happened and what it is I need to do to access these files please,