Need to save my files…..

Hi everyone,

I have a problem that I would like to share with you. I recently bought a hard disk and had formatted it on my friends system. The installation had no problems and I copied some software in that. But later I found that I could not read some of the files and without my knowing my friend formatted the disk. Now I have lost some important data and need to get back that in any case. Please do suggest some good tools which can help me get them back without much hassle.

Thanks in advance!!!