1) Check disk 
CHKDSK (short for `check disk`) is a system tool in DOS, OS/2 and Windows. It verifies the file system integrity of a volume and fixes logical file system errors. It is similar to the fsck command in Unix. On Windows NT operating systems, CHKDSK can also check the disk surface for bad sectors and mark them. (In MS-DOS 6.x and Windows 9x, this is.....
Check Disk