If the music files won't copy back directly try copying them onto a usb stick and move them back into the correct itunes library on your computer. file location will be something like itunes/itunes music/music.
Don't uninstall and reinstall itunes, try copying your original itunes music folder back to the itunes music folder. Then try playing one of your tunes - you may have to redirect itunes to the file location.
well it seems that when i tried to copy the music library to the external drive i moved them instead, including the folders which is why itunes couldn't find it. managed to copy the files back onto my computer but itunes still couldn't find them.
so i did as you said and told itunes to look in a different location! bleedin' obvious now innit?
had already reinstalled itunes, i do it fairly often as it seems to stop functioning properly once a few updates have been installed.
now works fine except that it now won't recognise my iphone! cuh, solve one problem, inherit another.
thanks for the advice stoney, at least i can listen to my music again!