Could you tell me if the hard drive is working normally after the chkdsk has finished? Using this command was a good decision because usually resolves file corruption problems. If some files are missing after the process you may need to use a data recovery tool in orded to save them. I stongly recommend you not to use the drive until you have the files recovered. There is a chance that you may overwrite the files if you keep copying new archives on the hard drive. This will make data recovery imposible. For further details are some software suggestions, please check the link below.
Hope this helps