Look at Zero Assumption Recovery since it's demo mode should tell you if it's worthwhile for this failure.
Also can I ask if this is a FAT32 volume? If so those will go missing.
I have an external harddrive and to troubleshoot the problem I installed the harddrive into my desktop and this is the error that I get: the disk structure is corrupted and unreadable. My questions is, will the chkdsk in Windows XP Home Edition fix this issue. My files are still there, I have ran the software to verify this, I just feel paying that much for a one time use of software is outragous. I just need to get the disk structure repaired so that I can retrieve the files. Is there some freeware or shareware out there in cyberspace that I can use to retrieve these files.