Imovie:Can't import dv footage directly onto external hd

[Mandy Claire Caulton]

Can anyone help?I've got an imac G3400 on osx10.2.6 and when i plug the 
camera the back of the external hd it imports onto my internal hd.The 
thing is, I can,t choose which hd it goes too.Both hds are on the 
extended format.I've ran out of ideas..THis is my first post i think !! 
so Hello everyone..I'm seriously stuck..