Itunes problem

I have recently transferred everything from an old imac to a new imac

Everything went ok

When i goto itunes all my music has a ! next to it asking me to locate the original file.

I do have these files backed up somewhere but why have they not transferred across and is there a way to rectify this without having to re-upload 50,000 songs?

Any help would be appreciated..

Was there a problem navigating to the location? Is it on an external drive? I think if you just identify where the files are, you're done. If that's what you did and it still asks next time, I'm not sure what your next step is.

iTunes is probably looking in the wrong place for your content. Launch iTunes, then go to Preferences>Advanced and make sure it has the right location for your media folder. That should fix the problem.