I'm trying to run Acronis True Image to backup my disk and get this error:

I click ignore, my PC hangs for a while and then works normally and backup is completed.
I have tried almost everything I can: chkdsk, SeaTools (my HD is from SeaGate). Nothing worked and I still get the same error.
How can I fix the bad sector?
chkdsk /f– Keltari Jun 02 '13 at 20:16