ok here goes...
This is what I would do to try and fix the problem:
1) copy all of my mp3's and the entire iTunes application, folders & data files onto my new hard drive
2) check to make sure iTunes works properly on the new hard drive
3) make an alias of the iTunes from my new hard drive and place it onto my main drive
4) check it out and see if iTunes runs properly from the alias
5) if all works well, trash the files from my main drive, as now I have it all on my new hard drive
Now theoretically this should work out fine. If u copy everything from iTunes, then your date files containing your playlist information will be there as well, hence no need to recreate playlists...