If it's a NTFS drive you might try the File Scavenger product from this company:
http://www.quetek.com/prod02.htm
No relationship to the company or anything, just a user. I've used it with great success but I suspect there are some situations that it can't handle but you never know....
Thanks very very much for this tip. After unsuccessfully downloading half a dozen prospective "disk recovery" programs I was just about to give up and reformat my data hard drive. Then I came across your posting and was encouraged because you specifically mentioned NTFS drives. I downloaded the File Scavenger demo and it immediately found my "missing" hard drive and all the files on it!! No other program got close.
I had to pay for a File Scavenger license to get it to recover them but it was $40 very well spent. All files now safely transferred onto my other drive. Phew !!
Highly recommended !!!