The command chkdsk /f detects and fixes errors on your hard disk, while chkdsk /r locates your drive's bad sectors and attempts to recover any readable data from them. Technically, the chkdsk /r command does the same thing as chkdsk /f, while also checking your drive's bad sectors. If you want to find and resolve logical disk errors, chkdsk /f will suffice, but you can also use chkdsk /r to find physical disk errors.