For private keys lets use example address B539KQtetSJRZo3JJLc1XRNEZRzGyVgU2W. So in this case ........
- Start your XBC wallet
- If it is locked just unlock it but uncheck "For staking only"
- Go to menu Help > Debug window > tab Console
- In bottom input box type the following line and press enter "dumpprivkey B539KQtetSJRZo3JJLc1XRNEZRzGyVgU2W"
- Write down code returned on few papers / files / whatever and keep it safe, that is private key for address B539KQtetSJRZo3JJLc1XRNEZRzGyVgU2W
- Later if your HDD fails again, computer ends up stolen or something like that just use "importprivkey privatekey label"
To import address to some other XBC wallet. Label is name for address that will be imported, it can be anything you want.