Hi…
When i join my external hd from my laptop, i got error message .
If u know plz explain me…
thz u for ur help.
This is my error msg.
http://img297.imageshack.us/img297/1249/errorl.png
Hmm. I think it pretty much tells you right there.
If you have windows, boot back up into windows and connect your drive. Wait a few seconds then PROPERLY DISCONNECT IT by choosing to safely remove hardware. Then disconnect it and boot up into linux. Connect the drive and you should be good to go! 
Good Luck,
Ian