From the help & support centre:
ChkdskCreates and displays a status report for the disk. The chkdsk command also lists and corrects errors on the disk.
The chkdsk command with the parameters listed below is only available when you are using the Recovery Console. The chkdsk command with different parameters is available from the command prompt.
chkdsk [drive:] [/p] [/r]
Parameters
none
Used without parameters, chkdsk displays the status of the disk in the current drive.
drive:
Specifies the drive that you want chkdsk to check.
/p
Performs an exhaustive check even if the drive is not marked for chkdsk to run. This parameter does not make any changes to the drive.
/r
Locates bad sectors and recovers readable information. Implies /p.
Note
The chkdsk command requires the file Autochk.exe. If it cannot find it in the startup directory (\%systemroot%\System32, by default), it will attempt to locate it on the Windows Installation CD. If you have a multiboot computer, be sure you are issuing this command from the drive containing Windows.
It should run on external drives.