external hard drive

I have been using a 320 gb seagate external hard drive for a few years now. It finally became full, so i got a new one. Long story short i transferred my music files to the new 1tb hard drive and changed my preferences so that itunes feeds from that drive. My problem is that even with every other app closed, i cannot eject my old hard drive without closing itunes as it says the drive (old hard drive) is still in use. i cannot figure out how to solve this problem, is there a way to figure out what exactly is still using this hard drive as a primary source.
thanks
Derek Hurt

i would shut down the computer and unplug the drive. restart and when something doesn't work you have isolated the program.

i have found that a very select few files 'cannot be located' on the new drive. therefore i am thinking that some did not transfer, so i tunes is still trying to communicate with the old device...any ideas.