I made the mistake of turning on Home Sharing in the iTunes version 9.1.3 (don't do this...).
The OSG family has about 10 computers lying around the home network, just waiting to pounce. In no time, my poor iTunes library was flooded with multiple copies of musical bilge - seriously what in heaven's name are those kids listening, too? (and Watching!!! - but that's another blog for another day...).
I found I had 12 versions of Dream On, , and Paperback Writer was written is 18 places on my drowning disk drive - I was Suddenly Numb (17 versions/copies).
I started to manually remove them - ever tried that in iTunes? About every 3rd delete it makes you confirm that you really, yes, really, I said REALLY, gd it!!, want to move the file to the recycle bin. Who wrote that damn feature? After 10 minutes I gave up - seriously considered deleting the whole thing and starting over...
Before pulling the red cord, I checked around online for an iTunes friendly deduper. Not an easy task if you run W7. A superstar named Doug Adams wrote some brilliant shareware script for this - "Corral iTunes Dupes AppleScript 7" - but it only runs on Apple. Molesoft will let you download a free version of Duplicate File Finder, but that only tells you the baby's ugly - it doesn't actually DO anything. You have to pay up if you want to actualy fix your problem. I have no problem paying for software - but it isn't worth $$ to me to dedupe iTunes. I am irritated, but not incapacitated.
I'd be a little more careful about the meta-data fixing - I think it munged a few different versions of same songs into one. I had about 10 legit verions of One Particular Harbor recorded live, old, new, at Fenway, in Hawaii - now I have one....bummer...but it only happened after I 'fixed' my meta and deduped. Be careful of the dreaded "Accept All" temptation...
There is also a function called File Inspector - didnt try it, have no idea what it does...
Overall - a great de-duper - and a super-de-duper iTunes library manager. And you only pay what you and your conscience think its worth.
oh - one more thing, remember to turn off Household Sharing before you dedupe or it will keep trying to reload copies from other computers on the network and you'll be forever swimming upstream.