I assume that the CCTV system runs via a PC.
Is you operating system installed on the master drive? Does Windows boot up at all?
If yes to both questions, then click on Start, Run and type in Chkdsk and press enter.
This program should isolate the bad sectors on your HDD.
if you can't boot up, then switch the Slave to become the master (and vice versa) and install your operating system onto the slave.
Once this is done, run the Chkdsk utility program to isolate the bad sectors. You will have to re-install all programs that you have on the existing master HDD.