external hard disk

hallo,

i have ubuntu 9.10 karmic koala.

so,
my external hard disk is called WD and it always worked so good on my linux until my friend came and connected his hard disk next to mine and we started exchanging files and films...
when i disconnected his and try to access mine this is the message:

Unable to mount My Book
>
> Error mounting: mount exited with exit code 13: $MFTMirr does not
> match $MFT (record 0).
> Failed to mount '/dev/sdb1': Input/output error
> NTFS is either inconsistent, or there is a hardware fault, or it's a
> SoftRAID/FakeRAID hardware. In the first case run chkdsk /f on Windows
> then reboot into Windows twice. The usage of the /f parameter is very
> important! If the device is a SoftRAID/FakeRAID then first activate
> it and mount a different device under the /dev/mapper/ directory, (e.g.
> /dev/mapper/nvidia_eahaabcc1). Please see the 'dmraid' documentation
> for more details.

well all my life in there!!