That's a little hard to understand. Is this a disk that already has data? Where is it "detected?" - is there a drive letter and an empty drive, or no drive letter, or a drive letter and garbage?
My best guess is that this is a job for recovery software, but I can't tell from the single sentence above. More detail would help.
Please don't defrag - if the disk is corrupted, that will guarantee that you won't recover data.