How do you reset the library of iTunes?

Question

I had to reload some music on my PC. Now all the old songs in iTunes are lost, and some are replaced. There are a lot of duplicates. How can I erase this and reinstall?

Answer 1

Start itunes. Either way:

1). Select and check all songs. Press delete.
2). Delete the playlist and recreate.

Answer 2

To get rid of duplicates you can press VIEW
then SHOW DUPLICATES