How can I delete Songs that can not be found?

[Compact]

For some reson iTunes decided to reset the location of my Music library from my extrenal HD to the My Docs one (maybe I turned iTunes on when extrenal HD was not connected).

Anyway, then it decided that it could not find half my songs.
SO
I decided to add the music folder again, thinking it would find duplicate songs and over-write in iTunes.
BUT
i now have 2 copies of all my songs in iTunes
1 that works and another which has the '!' logo next to it and cannot be found.
Is there a quick way to delete all these?
Maybe by searching for them or ordering them, so I can select all and delete easily?

I remember, maybe some tool for this, but cannot find it, cheers.

[Cold Irons]

Check out the sticky at the top of this forum - isolate ! songs for removal:
How to isolate missing tracks (exclamation mark)

[Compact]

cheers
must have been blind to miss that..

[heveyman]

Go to ..add a library
right click on each library in "Music" and select "remove library"
rename the folder that contains your music'
change the iTunes folder to that new folder name
Add the new folder name as a library
Organize the library and it will be clean