I remembered that I had some issue with copying some big files from the disk. It used to give me "Cant read from source file" error. So I thought now that issue might have become sever. I dont know what caused this issue, but I feel that it was due to bad sectors. Earlier I tried running chkdsk but no use. So what I did now is to cut paste all files in all drives to external hard disk using software called TeraCopy. The good thing is that if some files are unreadable, TeraCopy skips them and moves to copy next file. In the end it lists all files which had issue while copying. So in the end I got list of troubling files. To recover them, I first installed old version of EASEUS data recovery software and then deleted those files and then run EASEUS data resovery's recover deleted files wizard. It scans the disk listing recoverable files. I chose those troubling files and recovered them. However note that some files may not be recovered. For them EASEUS shows 0 KB size in its recovery wizard, even when you know they are videos. For me, when I put those files for recovery, my PC crashed to blue screen in multiple attempts. So this was clear indication that my old hard drive was dying. Finally, I tried doing formatting (not Quick Format) drives by right clicking the drive. However, it seems that it is taking really long. Its not over yet after several hours....Will update once I come to final conclusion.