A utility program in Windows that looks for lost clusters on the hard disk. It also reports the current amount of free memory and disk space. Originating with DOS, Chkdsk has remained as a command line utility in Windows. Running Chkdsk with the /f parameter (chkdsk /f) reclaims the lost clusters and turns them into .CHK files, which can generally be discarded. Running without the /f reports the current condition of the disk without "f"ixing anything.