I have external hdd pluggable via usb. It stopped working immediately. When I connect it to computer with Windows it hangs explorer for about 3 minutes. After this time I get message that disk has to be formatted before usage. Disk has single partition with NTFS file system. Chkdsk without params shows a lot of unreadable file segments. I never let it finish since it takes a lot of time. The question is whether should I try to run chkdsk with /f or /r? The priority for me is to recover data from the hard drive if possible. Does chkdsk overwrites corrupted sectors so that data cannot be recovered or it works more gently and recovers files to unused sectors? Next question is what does it mean when chkdsk shows unreadable file segments of different numbers everytime? If its logical issue it should show the same numbers of corrupted segments until I let it fix it. Am I right?