How do I not import duplicates?

[Steve]

  I have several disks of mp3's lying around that I want to import into 
my library. I think that most of the files on these disks, are in the 
library already, but I know that there are some that are not.

  If I just import all the files on the disks I would end up with 
hundreds of duplicates that would have to be manually deleted.

  Is there an easier way to do this?

Steve