questions about TV shows on an external HD

[UCLA Bruins Fan]

Hi Everyone,
I coppied my TV shows folder onto an external hard drive.  It achieved  
my goal which was to free up space on my internal drive, but, now,  
when I plug in my ipod I'm told that files can't be coppied because  
they can't be found. When I go to watch a TV show with the external  
hard drive I'm told that the origional file can't be found.  When I  
select the show on the external drive it coppies it back into my  
library on my internal drive.
Is this normal? Is there anything I can do to stop getting the message  
about files not being able to be copied when I sync my ipod?
Thanks as always, Olivia