Let's deal with the easy one first... there is a Union Jack flag on the Knoppix website, which takes you to an English version of the site. It's developed by a German (Klaus Knopper) which is why the default homepage is in German.
Now to the more tricky stuff... the normal command you'd use to test a hdd for errors is called fsck (file system check) - it's the Linux equivalent of chkdisk for Windows. However, I've never used it to check a hdd that's been partitioned with NTFS so I'm not sure if it will work.
Another alternative would be to use the command ntfsresize - fi /dev/hd## (replacing ## with whatever the drive is, e.g. /dev/hda1) which does some very basic checking of the drive, but it's not as in-depth as fsck/chkdisk. Run the command df (which displays the amount of disk space used per partition) or cfdisk (which is a version of fdisk), to display the drive's name if you're not sure of it.