itunes never recognises library

Hello eden58,

After reviewing your post, it sounds like you have your iTunes media saved to an external HD. I would recommend that you read this article, it may be able to help the issue.

Locate and organize your iTunes files - Apple Support

You can change the iTunes Media folder location to share music between accounts on the same computer.

1. Mac OS X: Choose iTunes > Preferences.
   Windows: Choose Edit > Preferences.
2. Click the Advanced pane.
   

In the Advanced pane, you can also:

• Make sure that you back up your media to your media folder. Click the check box next to "Copy files to itunes Media folder when adding to library."
• Reset your media folder to the default location (the iTunes folder). Click the Reset button next to the location box.
• Move your iTunes Media folder to a new location. Click the Change button next to the location box. After you change the location of the folder:
  • If you make a new or alternate iTunes library, the library will use the new location.
  • Existing files won't be moved unless you choose File > Library > Organize library and choose the option to "Consolidate files."

If you want to move your music to a new computer, see How to move your music to a new computer.

Thanks for using Apple Support Communities.
Have a nice day